MCB Lecture 25 Developmental Genetics Flashcards Preview

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Flashcards in MCB Lecture 25 Developmental Genetics Deck (39)
0

Describe the life cycle of drosophila

Egg
Embryogenesis
Larva
1st-3rd Instar
Moulting

Pupation
Adult

1

What are Homeotic genes?

These are genes responsible for the development of specific body parts

2

What is Ultrabithorax?

This is a Homeotic gene that results in the haltere being replaced by a second set of wings

3

What is antennapedia?

This is a gene that when mutated causes feet growing out of the antennae

4

What are HOX genes

These are Homeobox genes
This is a suite of 8 genes in drosophila

The genes are involved with development of body structures

5

Describe spatial expression of HOX genes

Different regions express different genes

6

Describe how segment identity can be determined by HOX mutants

HOX mutants indicate which region is controlled by that gene

7

What is a homeodomain?
How many are there in drosophila?

This is a protein coded for by a HOX gene

There are 8 in drosophila

8

What is special about the amino acid sequences in the 8 homeodomain proteins?

Between the 8 homeodomain proteins are consensus sequences that are identical or very similar.

9

What do the consensus sequences in the homeodomain proteins correlate to?

Three helices that are similar in all the homeodomain proteins

10

What do the variable regions in the amino acid sequences of the homeodomain proteins correlate to?

This corresponds to the regions of the protein outside the helices. This gives the 8 proteins their different functions

11

What is the function of homeodomain proteins?

The mediate binding of protein to DNA

12

Compare HOX genes in drosophila and mice

Number
Number of clusters
Order of genes

Number: dros: 8, mice: 39
Clusters: dros: 2, mice: 4
Order of the genes: same

13

Why is studying HOX genes in drosophila relevant to humans?

It is relevant because there has been much conservation of the genes from flies to humans

Things we find out about flies can been applied to human development

14

Compare HOX genes is drosophila and humans

Number of clusters
Gene duplications
Sequence correlating to body map?

Number of clusters: humans have many more
Gene duplication: only in humans; accounts for new functions
The mapping (order of genes to order in body plan) is seen in both flies and humans

15

What is the first step in development of a body plan?

Setting up the axes:
Posterior-anterior
Dorsal-ventral

16

Describe (in order) all the different types of developmental genes

Egg polarity genes
Gap genes
Pair rule genes
Segment polarity genes
Homeotic selector genes

17

What are egg polarity genes
Give an example

These genes set up the anterior-posterior axis of the egg

Bicoid

18

What are Gap genes?
Give examples

Gap genes set up the broad segments

Eg. Krüppel, Hunchback, Giant

19

What are pair rule genes?
Give examples

Pair rule genes set up more definite regions

Eg. even skipped, Ftz

20

What are segment polarity genes?
Give examples

Definition of segment
Eg. Gooseberry, engrailed

21

What are homeotic selector genes?

Define segment identity

22

What are maternal effect genes and why are they relevant to study of development?

Maternal effect genes are genes in the mother that affect only the offspring.

This individual's genotype does not affect their own genotype, but the offspring's

They are relevant because they solve the problem of lethality

23

Describe the phenotype of a homozygous mutant female fly

Why is this so?

Normal.

Because their mother was not homozygous mutant, so they received the required proteins.

24

What are the parental genotypes that result in a mutant fly?
Why?

The mother must be homozygous mutant to produce a mutant fly

25

What are the parental phenotypes that lead to normal fly development?

The mother must have at least one functional copy of the gene

26

Describe the problem of lethality

When studying genes to do with development, any homozygous mutants will probably not be viable

27

Why are maternal effect mutants useful?

Because they allow us to overcome the problem of lethality and see the affect when developmental genes do not function

28

Describe cell-cell sequential induction

Which type of gene is involved?

B -> A

The influence of B on A creates another region C

C influences A and B

These influences create areas D and E

Segment polarity genes and HOX genes

29

Describe the interaction between Egg polarity genes and Gap genes

The nurse cells set up the bicoid gradient from anterior to posterior end

Bicoid is an activator for Hunchback (gap).
So, high concentration of bicoid at the anterior end corresponds high concentration of hunchback at the anterior end


30

Describe the interaction between egg polarity, gap and pair rule genes

Bicoid, hunchback, Giant and Krüppel are activators and repressors from the Even skipped gene

31

In a pair rule gene (even skipped) enhancer, how many bicoid binding sites are there?

5

32

In a pair rule gene (even skipped) enhancer, how many giant binding sites are there?

3

33

In a pair rule gene (even skipped) enhancer, how many Krüppel binding sites are there?

3

34

In a pair rule gene (even skipped) enhancer, how many hunchback binding sites are there?

1

35

Which genes act as activators on the Even skipped gene enhancer?

Bicoid
Hunchback

36

Which genes act as repressors on the Even skipped gene enhancer?

Krüppel
Giant

37

Bicoid is a ... regulatory element.
It acts on ... Regulatory elements on ...

Trans acting

It acts on cis elements in the enhancer region of the Eve gene

38

Name a maternal effect gene

Which genes HOX genes are zygotic?

Maternal effect: bicoid

Zygotic: Krüppel, even-skipped, gooseberry

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