A Level Topic 3 (Gene Expression)

Front 1

Lactose is present

Back 1

1) regulatory gene Lac I produced the lac repressor

2) lactose binds to lac repressor > causes it to change shape & detach from the operator

3) no longer blocks > RNA polymerase is able to attach to the promoter

4) RNA polymerase transcribes for structural genes Lac A, Z & Y

5) synthesis of protein able to break down lactose > b galactosidase & lactose permease

5) protein breaks down lactose

Front 2

Lactose is not present

Back 2

1) regulatory gene Lac I produced the lac repressor

2) lac repressor attaches to the operator

3) blocks the promoter region > RNA polymerase unable to bind

4) RNA polymerase x transcribe for structural genes Lac A, X, Y

5 ) proteins (e.g. b galactosidase & lactose permease) x created that will break down lactose

(So no digestion of lactose)

Front 3

Promoter

Back 3

sequence of DNA bases at the start of a gene that RNA polymerase binds to

(Located before structural genes)

Front 4

Operator

Back 4

sequence of DNA bases that transcription factors bind to

Front 5

Structural genes

Back 5

Genes that code for useful proteins (e.g. enzymes)

Front 6

Regulatory gene

Back 6

Gene coding for an activator/ repressor

Front 7

Control elements

Back 7

Operator & promoter

Front 8

Activators

Back 8

Aid the binding of RNA polymerase > activate gene

Front 9

Repressors

Back 9

Stop RNA polymerase from binding > inactivate the gene

(Stops transcription initiation complex forming)

Front 10

What are epigenetic changes (Define + 3 marker)

Back 10

Attaching/ removing chemical groups to or from the DNA (without altering the base sequence of DNA)

1) methylation/ adding methyl grp to DNA

2) histone modification

3) (therefore) affecting gene regulation

Front 11

How does a stem cell become differentiated?

Back 11

1) all stem cells have SAME genes > not all are activated (so x expressed)

2) stimulus causes gene to become activated (others inactivated)

3) mRNA will only transcribe from active genes

4) mRNA is used to translate this into a protein

4) protein > modifies structure & function of the cell > cell becomes specialised & differentiates

Front 12

DNA methylation

Back 12

M for Mamura who repressed his feelings for her

1) attaches to the CpG site > where Cytosine & Guanine bases are next to each other in the DNA

2) adding methyl > changes DNA structure > transcription factors x bind to the gene > gene is repressed (inactive)

Front 13

Histone

Back 13

Protein that DNA wraps itself around to form chromatin which makes up chromosomes

Front 14

Histone modification (adding)

Back 14

NORMAL one

1) adding an acetyl grp > DNA wraps less tightly around histone protein/ chromatic less condense

2) RNA polymerase/ transcription factors can bind > gene is transcribed

3) Adding = Activated

Front 15

Histone modification (removal)

Back 15

NORMAL one

1) removing an acetyl grp > DNA is wrapped more tightly around the histone/ chromatin is more condense

2) RNA polymerase/ transcription factors are unable to bind > x transcribe gene

3) Removal = Repressed

Front 16

What is a methyl grp

Back 16

CH3

Front 17

What is an acetyl grp

Back 17

COCH3

Front 18

Epigenetic changes passed on

Back 18

1) Passed onto in daughter cells in mitosis/ meiosis

2) genes activated/ inactivated (as in the original cell)

Front 19

Homologous pairs

Back 19

Chromosomes that share

1) same structural features e.g. same size, centromere position

2) same genes at same loci positions (with dif alleles)

Front 20

How do sperm get to the egg (journey)

Back 20

1) sperm deposited high up vagina close to cervix

2) swim towards uterus & into oviduct

3) sperm swim towards egg in oviduct

Front 21

How are adult stem cells obtained (+ 1 disadvantages & advantage)

Back 21

1) obtained from body tissue e.g. bone marrow

2) operation, donor is anaesthetised as a needle is inserted into the centre of the bone

Little risk, may feel discomfort

Front 22

Ethical issues using embryos

Back 22

- procedure results in destruction of embryo that is viable (could become fetus if placed in womb)

- fertilisation = genetically unique individual with a right to life

Front 23

Use of stem cells should be allowed if

Back 23

- stem cells obtained from eggs x fertilised by sperm but activated artificially to start dividing > x survive past few days/ make fetus if placed in womb

- adult stem cells as no embryos destroyed