Exam 1 Review
Supplemental Instruction
Iowa State University / Leader: / Jacob Bonnstetter
Course: / BIOL/GEN 313
Instructor: / Dr. Rodermel
Date: / 09/13/16

Please note that this exam review does not cover everything that will appear on the test and not everything on this review will end up on the test. I have not seen the test, so I am just using my knowledge to best prepare you for what will likely be on the test.

  1. What are some of the implications of all organisms having similar genetic systems?
  2. That all life forms are genetically related
  3. That research findings on one organism’s gene function can often be applied to other organisms
  4. That genes from one organism can often exist and thrive in another organism
  5. All of the above
  6. Name and describe the three sub-disciplines of genetics.

Molecular Genetics-study of the structure and function of genes at a molecular level

Transmission Genetics-study of the transfer of genetic info to offspring

Population Genetics-study of genetic variation within a population

  1. Name some characteristics of model genetic organisms. Why are they important?

Short gestation period, numerous offspring, well understood organism, genome sequenced, easy to care for, adaptability to a lab environment

They are important because we can usually find the way something works in a simpler organism and apply that to something more complex

  1. Who proposed the concept of cell theory and what is it?

Schleiden and Schwann proposed that cells are the fundamental building blocks of living things, all living things are composed of cells, and cells arise from pre-existing cells.

  1. Briefly describe pangenesis and germ-plasm theory.

Pangenesis-genetic info from different parts of the body travels to the reproductive organs where it is transferred to gametes

Germ-plasm Theory-cells in reproductive tissues contain a complete set of genetic information

  1. Compare and contrast the following terms:
  2. Eukaryotic and prokaryotic cells

Prokaryotes: circular DNA, unicellular, no nucleus (nucleoid), no histone proteins

Eukaryotes: have histones, nucleus, multicellular, membrane bound organelles

Pg. 18 for more

  1. Gene and allele

Gene: a distinct sequence of nucleotides forming part of a chromosome

Allele: one of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome

  1. Genotype and phenotype

Phenotype: physical manifestation of a trait

Genotype: genetic code of an organism

  1. DNA and RNA

DNA: double-stranded, 2’ –H on ribose, Thymine

RNA: usually single stranded, 2’ –OH on ribose, uracil instead of Thymine

  1. DNA and chromosome

DNA is the double helix that wraps around histones which further condense and wind into fibers which further condense and wind to form a chromosome

  1. What were the major contributions from the following scientists:
  2. Meischer- discovered nuclein
  1. Kossel – discovered the 4 nitrogenous bases
  1. Levene – discovered the nucleotide(base + sugar + phosphate)
  1. Chargaff – discovered that A=T, C=G
  1. Watson, Crick, Franklin – W and C discovered the double helix with help from Rosalind Franklin’s X ray diffraction picture

Note: these are in order of their discoveries (ie. Meischer then Kossel etc.)

  1. What are Chargaff’s rules?

A=T, C=G

  1. Be familiar with the structure and numbering of the all five bases. Draw an example including the sugar and phosphate.
  1. Describe the three levels of DNA structure

Primary-sequence of bases

Secondary-double helix

Tertiary- how the double helix condense and winds into a chromosome

  1. Describe the structure of DNA. What are the components? What bonds are included?

Directionality (5’ to 3’) and antiparallel. Nucleotides are joined together by phosphodiester bonds and the two strands are joined by hydrogen bonds between the bases.

  1. What does competence mean?

The ability of a cell to take up exogenous DNA or RNA

  1. Define transformation

The ability of a cell to incorporate exogenous genetic material into its genome and transform

Important Experiments: Understand the experiment, not just the results. Be prepared to answer questions about what would happen if an aspect of the experiment were changed

  1. Outline Griffith’s experiment and the results.

Page210

  1. How did Avery, Macleod, and McCarty’s experiment test the transforming principle. Outline what they did and their results.

Page 210

  1. Outline the Hershey-Chase experiment.

Page 211-212

  1. Describe the Meselson and Stahl experiment. Be prepared to interpret their results for all 3 types of replication(conservative, semi-conservative, dispersive)

Page 235-236

  1. What is supercoiling? How does it come about? What is its purpose? What is the difference between positively supercoiled and negatively supercoiled?

Supercoiling is the winding of prokaryotic DNA to be more condensed. Positively supercoiled are over rotated (<10 bp per turn). Negatively supercoiled are under rotated (>10bp per turn)

  1. What are the 6 points of eukaryotic chromosome packing that we talked about in class?

Review slides from 9-2-2016 lecture

  1. Describe centromeres and telomeres. What are their functions and characteristics?

Centromeres-the point of the chromosome where spindle fibers attach. Helps DNA divide during cell division

Telomeres-the ends of DNA/chromosome that prevent degradation and allows the ends of DNA to replicate. Noted by the telomeric sequence (A or T)mGnwhere m=1-4 and n>1

  1. Label the 4 types of chromosomes

Metacentric submetacentric acrocentrictelocentric

  1. What is the c-value? Describe the c-value paradox.

c-value-amount of DNA in an organism.

c-value paradox: the amount of DNA in an organism does not correlate to the organisms complexity.

  1. Describe unique sequence, moderately repetitive and highly repetitive DNA. Include in your answer information about euchromatin and heterochromatin.

Unique: present only once or a few times, these are where most genes are located. This would be euchromatin parts of the chromosome

Moderately repetitive: typically 150-200bp that repeat thousands of times. Genes for ribosomal RNA and transfer RNAs; SINEs (short interspersed elements) and LINES

Highly repetitive :<10bp usually and repeats hundreds of thousands to millions of times. This would be centromeres and telomeres (heterochromatin)

  1. What are gene families?

A set of genes with similar functions that arose from a duplication of that gene in the past

  1. What proteins are involved in histone formation? Name them and how many of each. How many times does DNA wrap around a histone? How many base pairs does this take? How many base pairs in a nucleosome?

Octamer = 2x (H2A,H2B,H3,H4) this takes 147 bp and DNA wraps around the histone ~1.6x. H1 is the clamp that holds the DNA so it doesn’t unwind. This takes another ~20bp so the nucleosome is ~167 bp

  1. Why does DNA attach to histones?

DNA is negatively charged because of the phosphates in the backbone which are attracted to the positively charged histone because of the amino acids Lysine, and Arginine

  1. Describe the packaging of eukaryotic DNA.

DNA is packaged into histones which condense to form fibers which condense more to form a chromosome

  1. Be able to identify the following areas on a diagram of any model of replication.
  2. Origin
  3. Replication fork(s)
  4. Leading and lagging strand(s)
  5. Primers
  6. Okazaki fragments
  7. Template strands
  8. Polarity of both template and new strands
  1. Bacterial DNA replication takes place in what four stages? For each stage, name the enzymes associated with it.

Imitation: Initiator Proteins

Unwinding: Helicase, Gyrase, Single-strand binding proteins

Elongation: Primase, DNA pol I, DNA pol III, DNA ligase

Termination: Tus

  1. An active replication fork requires 5 basic components. What are they?

1-Helicase to unwind DNA

2- Single-strand binding proteins to keep strands from forming secondary structures

3-DNA Gyrase to relieve tension ahead of the fork

4-Primase to synthesize primers

5-DNA polymerases to synthesize strands

Draw the structures of the 4 DNA bases and Uracil (be able to number them as well)

Be able to count chromatid, chromosomes, linear DNA, centromeres, telomeres