Midterm 1 - Notes 6

Question 1

What percentage are protein coding regions in the human?

Answer 1

1.5%

Question 2

How are genes placed throughout the body

Answer 2

They are scattered

• flanked and interrupted by non-coding DNA
• very messy

Question 3

Are coding regions conserved or not conserved?

Answer 3

Conserved

- non coding regions are not

Question 4

How % do introns make up of the human genome?

Answer 4

20%

Question 5

The vast majority of Euk. have what?

Answer 5

Has no known function

• half is unique sequences (introns)
• other half is repeated sequences (junk DNA)

Question 6

What % of the human genome is transcribed?

Answer 6

75%

Question 7

What kind of change is histone modification?

Answer 7

Epigenetic change

Question 8

Repetitive sequences (3)

Answer 8

1. Long, but low copy
2. Short, but many local repeats
3. Intermediate length, scattered throughout the genome

Question 9

What does 80% of the human genome made up of? (4)

Answer 9

1. Transcribed
2. Associated with modified histones
3. Found in open chromatin areas
4. Binding transcription factors

Question 10

What do most Euk. have a large number of?

Answer 10

Transposons

Question 11

Transposons

Answer 11

A chromosomal segment that can undergo transposition

Question 12

What is another name for transposons?

Answer 12

Jumping genes

Question 13

What can lead to duplication of transposons? (2)

Answer 13

1. Excison

2. Reintegration

Question 14

What are the 2 major categories of transposons?

Answer 14

1. Tranpose as DNA (DNA transposons)

2. Transpose via RNA intermediate (retro-transposons)

Question 15

Transpose as DNA (4)

Answer 15

1. Involves transposase
2. Cut and paste mechanism
   - cut out a piece of DNA and reverses it and makes it back to intermediate
3. Can intergrate elsewhere into the genome at a random integration
4. Can become a stable part of it

Question 16

Transposase

Answer 16

Is an enzyme that binds to the end of a transposon and catalyzes the movement of the transposons to another part of the genome by a cut and paste mechanism or replicative transposition mechanism

Question 17

Transpose via RNA intermediate (retro-transposons) (3)

Answer 17

1. Involves reverse transcriptase and integrase
2. Copy and paste mechanism
3. Causes an amplification and duplication

Question 18

What was the study of discovery of transposons done on?

Answer 18

Maize

Question 19

Gene C

Answer 19

Necessary for kernel colour development

Question 20

What was c/c phenotype?

Answer 20

White kernels

- mutant

Question 21

What was C/C phenotype?

Answer 21

Purple kernels

- wildtype

Question 22

What kind of markers were used in the maize study?

Answer 22

Morphological markers

Question 23

What 2 things can happen when an Ac (a dominant allele) is present in c/c?

Answer 23

1. High frequency of revertants back to C/c
2. Revertants can affect whole kernel or only sectors
   - the earlier in development reversion happens, the larger the wildtype sector

Question 24

What caused the mutation in C-gene?

Answer 24

Integration of another genetic element called Ds

Question 25

What is reversion caused by?

Answer 25

Dissociation of Ds from C-locus

Question 26

What was the advantage to using maize?

Answer 26

Each kernel contains a seedling from one plant that came from the true parents

Question 27

When can Ds only move?

Answer 27

When Ac is present

Question 28

What can Ds and Ac both do?

Answer 28

Can change location in the genome

Question 29

What are Ds and Ac?

Answer 29

Transposons

Question 30

What element is Ds?

Answer 30

Non-autonomous

Question 31

What element is Ac?

Answer 31

Autonomous

Question 32

Excision of Ds during kernel development causes what?

Answer 32

Reversion to wildtype phenotype in affected sectors

Question 33

What does Ds not encode for?

Answer 33

Proteins for movement

Question 34

Can Ds be moved?

Answer 34

Yes

Question 35

What does the insertion of Ds into the genome disrupt? (2)

Answer 35

1. The C gene | 2. Effects kernel colour

Question 36

What does Ds cause when it moves?

Answer 36

A mix pigment of mutant and wildtype

Question 37

What did Barbar McMlintock discover?

Answer 37

Jumping genes and transposition | - 1940-1950s

Question 38

When did Barbar receive her nobel prize?

Answer 38

1983

Question 39

What are 4 reasons why Barbar did not receive her prize till 1983?

Answer 39

1. Peer discrimination - eccentric and a women 2. Study seemed only limited to maize - but then was expanded to bacteria 3. Only fully appreciated when it came on a larger scale 4. MAIN REASON = she miss interpreted her results as a regulatory mechanism, not as a random process

Question 40

Ds integration into C

Answer 40

A repressor of gene C activity

Question 41

Ac

Answer 41

A repressor of the repressor | - eg. an activator of gene C

Question 42

What was Barbars hypothesis? (3)

Answer 42

1. If Ds located away from target gene = no repression 2. Ac activates Ds translocation into target gene = repression 3. Ds translocation reversible by Ac action (dissociation) = no repression - all to do with gene control mechanism

Question 43

Did Barbars hypothesis hold true?

Answer 43

NOPE