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Miscellaneous > MCB Lecture 25 Developmental Genetics > Flashcards

MCB Lecture 25 Developmental Genetics Flashcards

0
Q

What are Homeotic genes?

A

These are genes responsible for the development of specific body parts

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1
Q

Describe the life cycle of drosophila

A 
Egg
Embryogenesis
Larva
1st-3rd Instar
Moulting

Pupation
Adult

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2
Q

What is Ultrabithorax?

A

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

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3
Q

What is antennapedia?

A

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

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4
Q

What are HOX genes

A

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

The genes are involved with development of body structures

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5
Q

Describe spatial expression of HOX genes

A

Different regions express different genes

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6
Q

Describe how segment identity can be determined by HOX mutants

A

HOX mutants indicate which region is controlled by that gene

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7
Q

What is a homeodomain?

How many are there in drosophila?

A

This is a protein coded for by a HOX gene

There are 8 in drosophila

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8
Q

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

A

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

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9
Q

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

A

Three helices that are similar in all the homeodomain proteins

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10
Q

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

A

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

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11
Q

What is the function of homeodomain proteins?

A

The mediate binding of protein to DNA

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12
Q

Compare HOX genes in drosophila and mice

Number
Number of clusters
Order of genes

A

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

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13
Q

Why is studying HOX genes in drosophila relevant to humans?

A

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

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14
Q

Compare HOX genes is drosophila and humans

Number of clusters
Gene duplications
Sequence correlating to body map?

A 
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
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15
Q

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

A

Setting up the axes:
Posterior-anterior
Dorsal-ventral

16
Q

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

A 
Egg polarity genes
Gap genes
Pair rule genes
Segment polarity genes
Homeotic selector genes
17
Q

What are egg polarity genes

Give an example

A

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

Bicoid

18
Q

What are Gap genes?

Give examples

A

Gap genes set up the broad segments

Eg. Krüppel, Hunchback, Giant

19
Q

What are pair rule genes?

Give examples

A

Pair rule genes set up more definite regions

Eg. even skipped, Ftz

20
Q

What are segment polarity genes?

Give examples

A

Definition of segment

Eg. Gooseberry, engrailed

21
Q

What are homeotic selector genes?

A

Define segment identity

22
Q

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

A

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
Q

Describe the phenotype of a homozygous mutant female fly

Why is this so?

A

Normal.

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

24
Q

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

Why?

A

The mother must be homozygous mutant to produce a mutant fly

25
Q

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

A

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

26
Q

Describe the problem of lethality

A

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

27
Q

Why are maternal effect mutants useful?

A

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

28
Q

Describe cell-cell sequential induction

Which type of gene is involved?

A

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
Q

Describe the interaction between Egg polarity genes and Gap genes

A

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
Q

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

A

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

31
Q

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

A

5

32
Q

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

A

3

33
Q

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

A

3

34
Q

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

A

1

35
Q

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

A

Bicoid

Hunchback

36
Q

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

A

Krüppel

Giant

37
Q

Bicoid is a … regulatory element.

It acts on … Regulatory elements on …

A

Trans acting

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

38
Q

Name a maternal effect gene

Which genes HOX genes are zygotic?

A

Maternal effect: bicoid

Zygotic: Krüppel, even-skipped, gooseberry

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