Cellular Control + Patterns Of Inheritance

Question 1

Define transcription factor

Define activator

Define repressor

Answer 1

Protein that binds to DNA
Switches genes on/off by changing rate of transcription

Starts transcription

Stops transcription

Question 2

What occurs if lactose present in ecoli (lac operon in E. Coli)
Where does lactose bind? 
What changes its 3D shape? 
What detaches from operator? 
What binds to operator? 
What begins?

Answer 2

Lactose binds to repressor 
Repressor changes its 3D shape 
Repressor detaches from operator 
RNA polymerase binds to operator 
Transcription of structural genes begin

Question 3

Define

intron

exon

Answer 3

Introns are a section of DNA that DOESN’T code for amino acids

Exons are a sequence of DNA that CODES for amino acids

Question 4

How is mature mRNA formed?

▪▪▪▪

Answer 4

During DNA replication both exons and introns copied into mRNA

This forms pre-mRNA

Introns removed from mRNA by splicing

Exons joined together after forming mature mRNA

Question 5

Name mutation types
▪▪▪

Which ones are frameshift

Answer 5

Substitution, insertion, deletion

Insertion and deletion are frame shift (affects way base sequence is read)

Question 6

Define a neutral mutation

Why does this occur?

What’s the most likely cause for this type of mutation?

Answer 6

A neutral mutation has no effect

It occurs as the amino acid triplet sequence is degenerate (one amino acid coded for by many triplets)

Substitution mutation

Question 7

Where do transcription factors bind in eukaryotes?

▪▪

Answer 7

Specific DNA sites

At start of target genes

Question 8

Define body plan

What is a Hox gene?

What are the highly conserved regions of hox genes called?

Answer 8

Body plan is the structure of an organism

Hox gene controls the development of the body plan

Homeobox sequence

Question 9

Why is mitosis and apoptosis important in controlling development of the body?

Answer 9

Genes that control both mitosis and apoptosis in certain cells can be controlled by transcription factors

This selects what genes are present

Question 10

What causes phenotypic variation?

▪▪

Answer 10

Genotype ~
Meiosis- independant assortment, crossing over and random gamete fusion

Environment ~
Climate
Diet
Lifestyle

Question 11

Define polygenic

Answer 11

Many genes control the phenotype and show continuous variation e.g. Skin colour

Question 12

What is etiolation

What is chlorosis

Answer 12

Plants grow abnormally long and spindly due to lack of sunlight

Plants don’t produce enough cholorphyll and turn yellow due to lack of mg in soil

Question 13

What is codominace?

Answer 13

When both alleles are dominant and expressed

Question 14

What’s the standard ratio for a dihybrid cross?

Answer 14

9:3:3:1

Question 15

What is autosomal linkage?

What does this mean for phenotypic ratio?
▪▪▪

Answer 15

When non sex chromosomes stay together during independant assortment

Phenotypic ratio will be different,

higher proportion of offspring has parents phenotype

Some different gametes still made from crossing over

Question 16

Define epistasis

What does recessive epistatic allele require?
▪
▪ ratio for homo recessive and homo dominant parent

What does a dominant epistatic allele require,
▪
▪ ratio for 2 homo dominant parents

Answer 16

Allele of one gene masks expression of another gene

2 copies of a recessive epistatic allele masks the expression of another gene, 9:3:4

Only one copy of a dominant epistatic allele masks expression of another gene,
12:3:1