3C: Differentiation & Variation

Question 1

what is gene expression

Answer 1

when the DNA code of a gene is used to make a protein

Question 2

what are transcription factors

Answer 2

proteins that bind to the DNA & affect the process of gene expression and regulate gene expression

Question 3

what is an operon

Answer 3

a unit made up of linked genes which regulate other genes responsible for protein synthesis

Question 4

what is the operon responsible for the digestion of lactose in E-Coli

Answer 4

Lac Operon

Question 5

which two enzymes help digest lactose to glucose

Answer 5

beta galactoside permease & beta galactoside

Question 6

when would the two enzymes needed to digest lactose be needed

Answer 6

when E-coli in in a environment with more lactose than glucose

Question 7

when are beta galactoside permease & beta galactoside made

Answer 7

when transcription of the lac operon takes place
- enzymes produced due to transcription and translation therefore glucose is produced due to digestion

Question 8

what is a promotor

Answer 8

RNA polymerase binding site
- starting point for transcription

Question 9

what is a operator

Answer 9

DNA binding site to repressor protein

Question 10

what is a repressor protein

Answer 10

binds to operator to block the promotor and therefore preventing transcription

Question 11

What happens to the E Coli lac operon is lactose is present

Answer 11

• lactose will bind to repressor protein
• repressor protein will change shape and is released from operator
• RNA polymerase can now freely transcribe the genes to produce mRNA which can be translated to form necessary enzymes which will digest lactose to produce glucose

Question 12

what does the repressor do?

Answer 12

attaches to operator and blocks transcription by blocking RNA polymerase

Question 13

what is epigenetics

Answer 13

how DNA interacts with smaller molecules within cells that can activate or deactivate genes
- Internal and/or external experiences that can influence gene expression patterns/ gene biochemistry

Question 14

what are the 2 intracellular systems that can interact to control epigenetic factors

Answer 14

• DNA Methylation
• Histone Modification

Question 15

what is DNA Methylation

Answer 15

the addition of a methyl at a CpG site by the enzyme DNA methyltranferase
- silences the gene by changing the arrangement of DNA molecule and prevents transcription

Question 16

what is Histone modification

Answer 16

caused by how tightly packed the DNA is packed around a histone due to how accessible DNA polymerase is to the DNA

too tight - less genes are transcribed due to less accessibility
too loose - more genes transcribed due to more accessibility

Question 17

what can affect epigenetics

Answer 17

stress
diet
medication
trauma / life events
mental health
activity levels
environmental pollutants

Question 18

how can epigentic changed be passed on through cell division

Answer 18

some changes are permanent therefore they are not affected or deleted by mitosis/ cell division bc the change is now part of the cells DNA - the gene is passed on to the daughter cells produced

Question 19

what are the 6 ways that genetic variation can be caused

Answer 19

• random fertilisation of gametes
• random mating between organisms
• meiosis crossing over
• meiosis independent assortment
• mutations
• interaction between genes and epigentics

Question 20

what are polygenetic traits

Answer 20

phenotypes that are controlled by multiple alleles
- skin color, intelligence

Question 21

what is a polygene

Answer 21

a gene that has too little effect on a phenotype by itself therefore it acts together with other gene loci on different chromosomes to produce observable variables

Question 22

what is demethylation

Answer 22

removal of a methyl group to turn gene back on allowing DNA to become mRNA through DNA polymerase

Question 23

what is acetylation

Answer 23

involved histone modification

loosens DNA wrapped around histones, allowing them to be transcribed and turn genes on