EOC Review Part 2: Heredity-Organisms Reproduce and Transmit Hereditary Information

EOC Review Part 2: Heredity-Organisms Reproduce and Transmit Hereditary Information

EOC Review Part 2: Heredity-Organisms reproduce and transmit hereditary information

SPI 3210.4.1 Identify the structure and function of DNA

SPI 3210.4.2 Associate the process of DNA replication with its biological significance

SPI 3210.4.3 Recognize the interactions between DNA and RNA during protein synthesis

SPI 3210.4.4 Determine the probability of a particular trait in an offspring based on the genotype of the parents mode of inheritance

SPI 3210.4.5 Apply pedigree data to interpret various modes of genetic inheritance

SPI 3210.4.6 Describe how meiosis is involved in the production of egg and sperm cells

SPI 3210.1.6 Determine the relationship between cell growth and cell reproduction

DNA and RNA: nucleic acids are composed of nucleotides; nucleotides are made of a phosphate group, sugar, and nitrogenous base

Draw and label a nucleotide for DNA and a nucleotide for RNA

Central Dogma of Biology: DNA -----(transcription)→RNA -----(translation)-----→Protein

DNA: deoxyribonucleic acid; it is double stranded and a twisted helix shape; it never leaves the nucleus (except when nucleus disappears during cell division); nitrogenous bases include (A) Adenine, (T) thymine, (G) guanine, and (C) cytosine; rules of base pairing say that G goes with C and A goes with T; purines (double ring structures pair with pyrimidines single ring structures); A and G are purines and C and T are pyrimidines; weak hydrogen bonds hold the pairs of nitrogen bases together and are easily broken; sugar is deoxyribose; contains instructions for production of all proteins for an organism

DNA Replication: DNA uncoils and each strand serves as a template to make a new copy; when the cell is not dividing the DNA is in the form of chromatin; when it divides the duplicated DNA forms duplicated chromosomes (sister chromatids); DNA helicase(uncoils), DNA polymerase(brings in new nucleotides), and DNA ligase(joins dna fragments called Okazaki fragments) are enzymes that facilitate copying of DNA

RNA: ribonucleic acid; single stranded and various shapes; leaves the nucleus; nitrogenous bases include (A) adenine, (U) uracil, (G) guanine and (C) cytosine; sugar is ribose; three types of RNA are (1) mRNA=messenger RNA (2) rRNA= ribosomal RNA (3) tRNA = transfer RNA

Protein synthesis: proteins are produced from the information in DNA; two parts (1) Transcription- mRNA is made from the sense strand of the DNA and carries the message out of the nucleus to the ribosomes and (2) translation-message carried by the mRNA is translated/decoded by the rRNA at the ribosomes to the sequence of amino acids needed to make the protein; tRNA (transfer RNA) transfers the amino acids from the cytoplasm to the ribosomes to construct the polypeptide or protein.

Copy and label diagram of DNA; Copy and label Protein synthesis diagram

Asexual vs. sexual reproduction:

Asexual reproduction: a single parent produces one or more identical offspring by dividing into two cells (mitosis or “binary fission in bacteria, “budding” in fungi); offspring are “clones” of parent (genetically identical); common form of reproduction in unicellular organisms; quick process that requires little energy; produces large number of offspring

Sexual reproduction: involves the production and fusion of two haploid sex cells (gametes) produced during a process called meiosis; sperm is the male cell and ova (egg) from the female join during a process called “fertilization” which results in a diploid cell called a “zygote”; usually will then reproduce cells to create a multicellular organism through mitosis; fertilization can be internal (dogs and people) or external (most fish); slow process that requires a great deal of cellular energy; few offspring are produced

Cell division:

Process of copying and dividing the entire cell; the cell grows, prepares for division, and then divides to form daughter cells; (1) mitosis/binary fission in bacteria and (2) meiosis

Cell cycle will include Interphase, mitosis and Cytokinesis

Interphase- longest phase of the cell cycle; the cell grows; normal activities and metabolism take place; duplicates the DNA and prepares for division

Mitosis- division of the nucleus of the cell

Prophase- duplicated chromosomes form by coiling of chromatin and spindle fibers appear; nuclear


Metaphase- duplicated chromosomes line up along the equator of the cell between spindle fibers

Anaphase-duplicated chromosomes pulled apart (chromatids) to opposite ends of the cell

Telophase-nuclear membrane reforms around chromosomes at each end of the cell; spindle fibers

disappear; chromosomes uncoil to chromatin

Cytokinesis: division of the plasma membrane and cytoplasm; two daughter cells are formed with exact genetic information

Results of mitosis are two daughter cells(body cells or somatic cells) with the same number of chromosomes as original cell (humans this number is 46); these cells are called diploid and contain two of every chromosome (23 pairs in humans)

Meiosis: consists of two cell divisions, but only one DNA replication; often referred to as “reduction division”; each cell division has prophase, metaphase, anaphase, telophase and Cytokinesis; only one interphase at the beginning; only occurs in the formation of sex cells (gametes); each are genetically unique thanks to crossing over and independent assortment of the chromosomes.

First division: produces cells with the have number (1/2) chromosomes but all are still duplicated

Second division: produces a total of 4 haploid cells (one of every chromosome)= sex cells (gametes)

These sex cells (sperm and egg) unite during fertilization to form a zygote (diploid cell) that will develop into an individual organism

Copy diagrams and information for mitosis and meiosis

Genetics: the branch of biology hat deals with inheritance of traits from generation to generation (heredity)

Gregor Mendel experimented with sweet pea plants in the 1800s; he is known as the Father of Modern Genetics.

Trait-characteristic an individual receives from its parent(s)

Gene- segment of DNA that carries instructions responsible for expression of traits; different forms of a gene are called “alleles”

Homozygous- refers to two alleles of a pair that are identical in the zygote (ex. BB or bb) “purebred”

Heterozygous- refers to two alleles of a pair that are different in the zygote (ex. Bb) “hybrid”

Dominant- controlling allele; covers or hides the other allele for a trait; represented by capital letter

Recessive- hidden allele, designated with a lower case letter

Genotype- genetic makeup of an organism; type of genes received (ex. Bb, BB, or bb)

Phenotype- physical appearance of an organism (ex. Brown or white)

Monohybrid- cross involving one trait (use small Punnett square 4 boxes)

Dihybrid- cross involving two traits at the same time (use large Punnett square 16 boxes)

Copy sample Punnett squares

Punnett square- graphic organizer to show the probable results of a genetic cross (mating)

Pedigree chart- graphic organizer to map genetic traits from generation to generation

Autosomal recessive: trait occurs equally in both sexes; trait tends to skip a generation;

affected offspring usually born to parents that are unaffected (normal); if both parents

are affected then all the offspring must have it as well

Autosomal dominant: trait occurs equally in both sexes; does not skip a generation;

if offspring has it at least one parent should be affected as well; if neither parent has the trait then none of the offspring can be affected

Sex-linked recessive: occurs more frequently in males than females; affected males usually have unaffected mothers; appears to skip a generation; never passed from father to son because it is on the X chromosomes; if a girl is affected her father had to be affected too

Y-linked: only males can be affected because it is on the Y chromosome; if the father is affected then all of his sons must be affected as well; does not skip a generation

Copy pedigree charts and analyze

Karyotype- chart of chromosomes of an individual grouped in their homologous pairs to study chromosome number/disorders (like Down’s syndrome trisomy 21-extra chromosome)

(turners syndrome- monosomy- missing and x in a female)

Copy the karyotype; is the individual a boy or a girl? Any abnormalities?

Test Cross- mating of an individual of unknown genotype (either pure for dominant or hybrid) with and individual of known genotype (pure recessive) to help determine the unknown

genotype (if hybrid some recessives will be present in offspring, no recessives = pure)

Mendel’s Laws of Inheritance:

(1) Law of dominance says that the dominant allele will prevent the other allele (recessive) from being expressed

(2) Law of segregation says that gene pairs separate when gametes (sex cells) are formed

during meiosis; each cell will only have one allele of each gene pair

(3) Law of independent assortment says that different pairs of genes separate independently of each other when gametes are formed during metaphase/anaphase II of meiosis

Patterns of inheritance:

Sex chromosomes are the 23rd pair; XX = female XY= male

Sex-linked traits are traits with a gene located on either the X or Y chromosome and is therefore associated with a particular gender (male or female); examples of traits: colorblindness, patterned baldness, and hemophilia

Linked traits are those whose genes are close together on the same chromosome and are therefore usually inherited together; ex. Red hair and freckles

Multiple alleles occur when there are more than two alleles for a given trait (blood type A,B, O)

Polygene inheritance is when one trait is controlled by many genes; ex. Height, skin color, hair color range of phenotypes gradually changes.

Codominance is where homozygous parents for different traits result in offspring that show both traits equally; black chicken crossed with white chicken produces a checkered chicken

Incomplete dominance is where the hybrid results in a phenotype that is in between the two phenotypes of the pure individuals; red crossed with white produces a pink offspring

Variation in offspring can be attributed to:

(1) crossing over- genes from one chromosome are exchanged with genes from another chromosome

Occurs regularly during meiosis (prophase I)

(2) nondisjunction- during meiosis the homologous pairs of chromosomes don’t separate; results in cells that either have an extra chromosome or missing a chromosome; if fertilization occurs the zygote formed will have a trisomy (extra chromosome like Downs) or monosomy (missing a chromosome like Turners)

(3) Independent assortment of chromosomes as they are lined up during meiosis II; random

Mutations are changes in the genetic code; only passed to offspring if occur in gamete (sex cell); most mutations have no effect; can be spontaneous of caused by mutagens (ex. Radiation, chemicals)

Gene mutations will affect only one gene; frame shift or substitution; can be missense, nonsense, silent mutations

Chromosome mutations affect many genes on a chromosome- inversion, translocation, deletion,

Duplication, etc.

Look at chart for mutation types. You do not need to copy this into your notes but should make

Make notations for each type that will help you remember them.


Figure 8 4 Different types of mutations

1. Which statement describes the structure of DNA? (c)

a. a single strand of amino acidsb. a single strand of nucleotides

c. a double strand of nucleotidesd. a double strand of amino acids

2. DNA is the information storage molecule of the cell. This infomraiton provides the instructions to produce molecules used for cellular activities. Which diagram best illustrates the translation of DNA’s encoded instructions? (d)

3. If one side of the DNA reads AGAGTC then what will the other side read? (TCTCAG)

4. Growth rate, length of bones, muscle structure, andhormone levels may all affect human height. Each of these factors is controlled by many different proteins in body cells. What type of gene relationship controls human body height? (polygeneintheritance)

5. DNA is replicated during the interphase of the cell cycle. Which event is needed to ensure the normal number of chromosomes is present in both daughter cells? (mitosis- division of the nucleus)

6. DNA transcribes the information for protein synthesis in mRNA. Where does the process of transcription take place? (in the nucleus)

7. Proteins are produced during translation. Which molecule carries the protein code that is translated? (mRNA)

8. Hemophilia is a sex-linked genetic disease. If a male with hemophilia and a homozygous normal female have a female child, what is the probability that the child will be a carrier for hemophilia? (0%)

9. In snapdragons, if white flowers are crossed with red flowers, all the offspring have pink flowers. When two pink snapdragons are crossed, some offspring have white flowers, some have red flowers, and some have pink flowers. Which inheritance pattern do snapdragon flowers exhibit? (incomplete dominance)

10. What pattern of inheritance is shown in this pedigree? (autosomal dominant)

11. Gametes contain hald the number of chromosomes that other cells in the body contain. When are gametes produced in organisms? (during meiosis)

12. Why is meiosis important for sexual reproduction? (meiosis reduces the number of chromosomes)

13.Chronic myeloid leukemia is caused by a chromosomal mutation. An example of this mutation is shown in the diagram. What type of chromosomal mutation causes myeloid leukemia? (translocation)

14. Which process is attributed to causing an additional 21st chromosome in a human karyotype? (nondisjunction)

15. Through scientific research, genetic technologies have advanced the study of gene sequences. Which is a main benefit of gene therapy technology? (a)

a. the ability to cure genetic diseases by replacing defective genes

b. the ability to genetically design organsisms that have never existed

c. understanding how human genes turn on and off to make carbohydrates

d. making genetically superior plants and animals to benefit the entire world

16. The bases in DNA pair by chemical interactions. How are the base pairs formed differently between the pairs? (a)

a. adenine and thymine form two hydrogen bonds, while cytosine and guanine form three hydrogen bonds

b. adenine and thymine form three hydrogen bonds, while cytosine and guanine form two hydrogen


c. adenine and thymine form covalent bonds, while cytosine and guanine form hydrogen bonds

d. adenine and thymine form hydrogen bonds, while cytosine and guanine form covalent bonds

17. DNA contains four different nitrogenous bases. Which base always pairs with guanine in the DNA molecule? (cytosine)

18. A portion of DNA is transcribed into the mRNA sequence AUGUCAAGCGUA. The table below shows the amino acids that correspond to codons in an mRNA sequence. Decode the mRNA sequence.


19. What meiotic stage produces the haploid condition of the four daughter cells? (division 1)

20. What is the end result of meiosis? (four haploid cells)

21. What event during meiosis introduces genetic variation between parents and offspring? (crossing over)

22.In the United States, it is possible for discoverers of gene sequences in organisms to patent those sequences. This gies the discoverer property rights for the sequences. Many scientists object to this practice. Which is the strongest argument against allowing a gene sequence to be patented? (c)

a. Patenting sequences prevents the sequences from being expressed in nature.

b. Patenting sequences prevents the sequences from being used in genetically modified organisms.

c. Patenting sequences prevents researchers from studying and creating innovations from the patented sequences.

d. Patenting sequences prevents conservationists from understanding the ecological needs of organisms from which the patented sequences come.

23. There is broad public debate on the ethics of performing research on human stem cells to find cures for human diseases. Which statement describes an ethical issue about the use of human stem cells for research? (a)

a. Some research focuses on stem cells obtained through the destruction of human embryos.

b. Any treatments discovered through such research would likely be too expensive for many.

c. Some research focuses on therapies that would only benefit the person from whom the stem cells came.

d. Any treatments dsicvoered through such research would be more effective in treating some patients than others.