16-genetics

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position of gene on a chromosome

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Biology

12th

35 Terms

1

position of gene on a chromosome

(gene) locus

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2

independent assortment

ability for any allele to be found in any cell

<p>ability for any allele to be found in any cell</p>
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3

3 factors affecting genetic variation

  • crossing over,

  • independent assortment,

  • random fertilisation

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4

when does independent assortment happen

metaphase 1

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5

when does crossing over happen

prophase 1

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6

F1 generation

offspring when 2 differently homozygous individuals are crossed, always heterozygous (e.g. AA x aa = Aa)

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7

F2 generation

offspring when 2 of the F1 are crossed

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8

test cross

crossing of an unknown with one showing recessive phenotype

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9

how does proximity of gene loci affect crossing over

increasing distance increases probability of crossing over

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10

sex linkage definition- which sexes of offspring cannot inherit from which parent?

  • gene found on X or Y chromosome (e.g. factor VIII, causing haemophilia, is on X chromosome)

  • if X linked, male offspring cannot get it (X from mother, Y from father)

  • if Y linked, female offspring cannot get it (XX)

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11

typical ratio of dihybrid cross (both heterozygous)

9:3:3:1

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12

epistasis

2 or more genes on different chromosomes affect the same feature

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13

autosomal linkage

2 or more genes on the same non sex chromosome

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14

how does crossing over interact with autosomal linkage

recombinants made- linkage broken by crossing over

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15

location of crossing over

chiasmata

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16

how could an allele cause a specific phenotype? (2)

  • enzyme not coded for- enzyme cascade disabled,

  • shift in protein structure (e.g. sickle cell anaemia) or no protein made

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17

genetic sequence causing Huntington’s disease

  • repeated CAG triplets- HTT gene on chromosome 4 coding for huntingtin

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18

genetic sequence causing haemophilia

  • f8 gene- codes for coagulation factor 8, abnormal allele results in abnormal/less/absence of factor 8

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19

Le/le effects on plants- what makes abnormal and how is it treated? (3)

  • Le codes for enzyme for synthesis of gibberellin,

  • le, recessive, produces non functional,

  • lele is dwarf plant, treated by applying gibberellin

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20
<p>A and purpose</p>

A and purpose

promoter region for regulatory gene/lacI- binds to RNA polymerase for transcription of lacI

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21
<p>B and purpose</p>

B and purpose

lacI- regulatory gene coding for repressor protein to bind to operator region

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22
<p>C and purpose</p>

C and purpose

promoter region for structural genes- binds to RNA polymerase for transcription of structural genes

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23
<p>D and purpose</p>

D and purpose

operator region- repressor protein binds so RNA polymerase cannot bind to structural gene promoter

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24
<p>E and purpose</p>

E and purpose

lacZ- codes for B-galactosidase to hydrolyse lactose → glucose/galactose

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25
<p>F and purpose</p>

F and purpose

lacY- codes for lactose permease to make cell more permeable to lactose

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26
<p>G and purpose</p>

G and purpose

lacA- codes for transacetylase

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27
<p>which parts of this belong to the lac operon?</p>

which parts of this belong to the lac operon?

C, D, E, F, G (structural gene promoter, operator, and 3 lac genes)

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28

What happens to the lac operon when lactose is taken up by a bacterium? (3)

  • lactose acts as effector molecule and binds to repressor protein,

  • lactose distorts protein shape and preventing it from binding to the operator site,

  • mRNA binds to promoter region and structural genes are transcribed, allowing for breakdown of lactose

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29

structural gene

gene coding for production of a protein used by a cell (could be actual structures or enzymes)

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30

regulatory gene

gene expression controlled by other genes close to it (on the same DNA molecule)

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31

inducible enzyme

enzyme synthesised only when substrate present

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32

repressible enzyme

binding of effector to repressor helps it bind to operator, stopping transcription- enzyme synthesised when substrate is not present

<p>binding of effector to repressor helps it bind to operator, stopping transcription- enzyme synthesised when substrate is not present</p>
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33

in which organisms are operons found

prokaryotes

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34

transcription factor definition- in which organisms are they found

protein binding to DNA at a promoter sequence affecting transcription (could increase or decrease rate)- only eukaryotes

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35

how does gibberellin stimulate amylase production (5)

  • DELLA proteins are repressor proteins and bind to PIF (transcription factor),

  • PIF cannot bind to promoter of amylase gene,

  • gibberellin binds to receptor and enzyme, DELLA breaks down,

  • PIF no longer bound to DELLA and binds to promoter region,

  • amylase gene transcribed

<ul><li><p>DELLA proteins are repressor proteins and bind to PIF (transcription factor),</p></li><li><p>PIF cannot bind to promoter of amylase gene,</p></li><li><p>gibberellin binds to receptor and enzyme, DELLA breaks down,</p></li><li><p>PIF no longer bound to DELLA and binds to promoter region,</p></li><li><p>amylase gene transcribed</p></li></ul>
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