Cellular control

Question 1

what is transcriptional level control

Answer 1

when gene expression is controlled by altering the rate of transcription of genes

Question 2

what are transcription factors

Answer 2

proteins that bind to DNA and switch genes on or off by increasing or decreasing the rate of transcription

Question 3

what are factors called that start transcription

Answer 3

activators

Question 4

what are factors called that stop transcription

Answer 4

repressors

Question 5

in prokaryotes control of gene expression often involves transcription factors binding to what

Answer 5

operons

Question 6

what is an operon

Answer 6

a section of DNA that contains a cluster of structural genes that are all transcribed together as well as control elements and sometimes a regulatory gene

Question 7

what do structural genes do

Answer 7

code for useful proteins such as enzymes

Question 8

what do the controls meets contain

Answer 8

promoters (a DNA sequence located before the structural genes that RNA polymerase binds to and an operator (a DNA sequence that transcription factors bind to

Question 9

what does the regulatory gene do

Answer 9

codes for an activator or repressor

Question 10

how does the lac operon function when lactose is not present

Answer 10

regulatory gene produces lac repressor
this then binds to the operator site where no lactose is present
this blocks transcription as RNA polymerase can’t bind to the promoter

Question 11

how does the lac operon function when lactose is present

Answer 11

lactose binds to the reposer, changing its shape so it can no longer bind to the operator site
RNA polymerase can then begin transcription in structural genes

Question 12

what is the lac operon, where is it found and what does it do

Answer 12

where the genes are found that produce enzymes needed to respire lactose
found in E coli

Question 13

what is post-transcriptional level control

Answer 13

when control of gene expression takes place after post-transcriptional level and mRNA is edited

Question 14

what are the sections of DNA called that don’t code for amino acids

Answer 14

introns

Question 15

what are the sections of DNA called that do code for amino acids

Answer 15

exons

Question 16

what are mRNA strands called that contain introns and exons

Answer 16

primary mRNA transcripts

Question 17

what happens during ‘splicing’ and where does it take place

Answer 17

introns are removed from the primary mRNA and exons are joined together to form mature mRNA
nucleus

Question 18

some proteins have to be activated after they are made what is an example of this

Answer 18

cAMP (post-transcriptional level control)

Question 19

what is the name for genes that control body plan development

Answer 19

Hox genes

Question 19

what are homeobox sequences

Answer 19

regions on how genes which are highly conserved so have changed very little during the evolution of different organisms that possess them

Question 19

mutations can be either

Answer 19

beneficial or harmful

Question 19

what is substitution

Answer 19

one or more bases are swapped for another base

Question 20

what is deletion

Answer 20

one or more bases are removed

Question 21

what is insertion

Answer 21

one or more bass are added

Question 22

what is a frameshift mutation

Answer 22

when insertion or deletion changes the way the rest of the base sequences is read

Question 23

why may a mutation have a neutral effect on an organism

Answer 23

a base is changed in the triplet but the amino acid it codes for doesn't change the new triplet code codes for a different protein but it is chemical similar to the function of the original one the mutated triplet code codes for something not involved in protein function

Question 24

what is continuous variation

Answer 24

when individuals of a population vary within a range, no distinct categories

Question 25

what is discontinuous variation

Answer 25

when individuals vary within distinct categories

Question 26

how does variation in the phenotype occur

Answer 26

same genes but different alleles crossing over and independent assortment differences in environment

Question 27

what is a polygenic characteristic

Answer 27

characteristic influenced by many genes, shows continuous variation

Question 28

what is a monogenic characteristic

Answer 28

characteristics influenced by one gene, shows discontinuous variation

Question 29

what is an allele

Answer 29

different versions of the same gene

Question 30

what is a gene

Answer 30

a sequence of bases on a DNA molecule that codes for a protein

Question 31

what is genotype

Answer 31

the alleles an organism has

Question 32

what is a phenotype

Answer 32

the characteristics produced by an organisms alleles

Question 33

what does homozygous mean

Answer 33

when an organism contains two copies of the same allele

Question 34

what does heterozygous mean

Answer 34

if an organism contains two different alleles

Question 35

what are codominant alleles

Answer 35

alleles that are both expressed in the phenotype cause neither one is recessive

Question 36

what is a carrier

Answer 36

a person carrying an allele which is not expressed in phenotype but can be passed on to offspring

Question 37

what phenotypic ratio would you expect for a monogenic genetic diagram

Answer 37

3:1

Question 38

what are dihybrid crosses used for

Answer 38

used to show the likelihood of offspring inheriting certain combinations of the two characteristics from particular parents

Question 39

what ratio do you expect from a dihybrid cross

Answer 39

9:3:3:1

Question 40

what does it mean if a characteristic is sex linked

Answer 40

the alleles that code for that characteristic are found on the sex chromosome

Question 41

what is epistasis

Answer 41

when the allele of one gene masks the expression of the alleles of other genes

Question 42

what is an autosome

Answer 42

a chromosome that is not a sex chromosome

Question 43

what ratio would you expect for a dominant epistatic allele cross diagram

Answer 43

12:3:1