Lecture 3

Front 1

1. What are the two different types of natural genetic flow? Define each.

Back 1

Natural genetic flow: how genes moved within the population
Vertical transfer: movement of genes from parent to offspring
Horizontal transfer: between organisms (plasmids in prokaryotes, viruses)

Front 2

2. Which type of gene transfer occurs in bacteria? What about in sexually reproducing organisms?

Back 2

Bacteria utilize both horizontal (via plasmids & bacteriophage viruses) and vertical gene transfer
Sexually reproducing organisms use vertical gene transfer

Front 3

3. During vertical transfer, what three processes can lead to a high degree of potential genetic variability of offspring? (Be sure to understand the details of each process and how they contribute to genetic variability.)

Back 3

Independent assortment of chromosomes: homologs randomly oriented in metaphase I, anaphase randomly assorts them into daughter cells; 2n combinations when n-> haploid chromosome # (in germ cells)
Random fertilization: any sperm fuses with any egg; 8.4 million chrom possibilities from each (8.42)
Crossing over: combines DNA from 2 parents into 1 chromosome; prophase I of meiosis

Front 4

4. What are the five processes that can lead to new genes? List and define each.

Back 4

1. Mutation: errors in nucleotide sequence. 2. Gene duplication: region of DNA duplicated; allows one gene to diverge for new function. 3. DNA Shuffling: reassortment during crossing over; different genes combined to form new genes with new functions. 4. Horizontal transfer: genes transferred between organisms like in bacteria. 5. Transposable elements: DNA pops out and re-inserts itself into a new gene -> new gene function or disruption of adopting gene

Front 5

5. Is there currently a cellular mechanism for the generation of brand new DNA (and, therefore, new genes)?

Back 5

No, new genes from pre-existing genes

Front 6

6. When does DNA shuffling occur? What functional outcome can occur when DNA shuffling combines two genes?

Back 6

DNA shuffling occurs during crossing over in prophase I during meiosis
When DNA shuffling combines two genes, a new gene can form with hybrid functions OR the adopting gene can lose function.

Front 7

7. Explain the significance of gene duplication in the generation of new genes. How can gene duplication lead to gene families?

Back 7

Gene duplication provides genetic novelty; with one gene performing its normal function, the other gene can mutate and change to create a new but related function
Multiple gene duplications allow for multiple gene divergences and a suite of related genes

Front 8

8. There are more than 200 gene families that are common to all three of the primary domains of life. What does that say about the rough number of functions or activities that are common to all three of the primary domains?

Back 8

This says that there are about 200 gene families that are responsible for critical/basic cell function and these gene families have been conserved through time
Most families perform replication, transcription,, translation and amino acid metabolism

Front 9

9. Explain why modularity of structure is common in proteins from the same gene family. (Be sure to understand what ‘modularity of structure’ means.)

Back 9

Modularity of structure means that the proteins belonging to a gene family have similar 3-dimensional structures.
Proteins from the same gene family will have similar sequences, therefore similar functions, and therefore similar structures.

Front 10

10. What mechanisms can cause disruption or loss of existing genes? (Be sure to understand how each mechanism leads to loss.)

Back 10

1. DNA Shuffling: reassortment during homologous recombination (crossing-over)
2. Unequal crossing over: gene duplication on one strand & gene loss on the other
3. Transposable elements: can remove pieces of chromosome with it & disrupt the genes it is inserted into
4. Mutation: missense, nonsense & frameshift

Front 11

11. What is the most common source of DNA mutation?

Back 11

Error during DNA replication (1 bp every 10,000) -> proofreading corrects all but 1 in 1,000,000,000

Front 12

12. List and define the four different types of DNA mutations.

Back 12

1. Silent: no change in amino acid sequence -> typically in wobble position
2. Missense: changes amino acid sequence -> may still produce functional protein if similar amino acid (charge, polarity)
3. Non-sense: amino acid changes to stop codon -> almost always non-functional protein produced (location on read)
4. Frameshift: addition/deletion of one or two nucleotides

Front 13

13. Mutations that become part of the multicellular genome must occur in the cells of the germ line. Why?

Back 13

Germ line cells are the only ones that are transferred to progeny

Front 14

14. Somatic mutations might affect the individual but cannot affect the population. Why?

Back 14

Somatic cells are not passed on during reproduction. In order to affect the population the mutation must occur in a germ cell.

Front 15

15. Low rates of mutation can result in high rates of evolution in single-celled organisms. Why?

Back 15

Single-celled organisms reproduce at a very high rate with a high number of offspring. These short generation times speed up the rate of evolution.

Front 16

16. What is ROS? (Where does it come from and what does it cause?)

Back 16

Reactive Oxygen Species: chemically reactive molecules containing oxygen species
Generated endogenous metabolic processes or exogenous “insults” (smoking, X-rays, pollutants)
Causes: gene shuffling, inactivation, altered regulation, or duplication

Front 17

17. What are transposable elements and how can they create new genes?

Back 17

Transposons: mobile DNA sequences that colonize genomes and move around within them
Can create new genes by integrating with host gene segments & fusing with them

Front 18

18. Both loss and gain of DNA occur ______________. The relative rates determine a species’ ____________________.

Back 18

constantly; genome size

Front 19

19. The Fugu genome is surprisingly small. Why do scientists think its genome is so small?

Back 19

The Fugu genome has lost DNA at a higher rate than it has gained DNA