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AL Biology > 16) Inheritance > Flashcards

16) Inheritance Flashcards

1
Q

define homologous pairs of chromosomes

A
  • same genes located at the same loci
  • same size/length
  • same shape/ position of centromere
  • same banding pattern
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2
Q

what type of chromosomes are homologous

A

autosomes (chromosome pairs 1-22)

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3
Q

what type of chromosomes are not homologous

A

sex chromosomes (pair 23)

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4
Q

what is haploid

A
  • ONE complete set of chromosomes
  • n (number of) chromosomes
  • not in homologous pair
  • each chromosome diff in size/shape/genes
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5
Q

what is diploid

A
  • TWO complete sets of chromosomes
  • 2n chromosomes
  • eg: humans 2x23 = 46
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6
Q

why must no. of chromosomes be halved before fertilisation / the need for reduction division

A
  • to maintain chromosome diploid number
  • from parents to offspring
  • to give genetic variation in gametes
  • too many extra sets of chromosomes cause problems
  • reduction division produces gametes
  • gametes fuse to form zygote
  • zygote has maternal & paternal chromosomes
  • gametes are haploid
  • so zygote is diploid
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7
Q

what is bivalent

A

a pair of homologous chromosomes

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8
Q

what is chiasma

A

point at which crossing over occurs

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9
Q

describe prophase I

A
  • chromosomes condense
  • homologous chromosomes pair up = bivalents
  • crossing over
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10
Q

describe metaphase I

A
  • spindle fibres attach to centromeres
  • homologous pair of chromosomes (bivalents) line up at the equator
  • random assortment of bivalents
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11
Q

describe anaphase I

A
  • spindle fibres contract to pull centromeres towards pole
  • one of each pair of chromosomes to either end/pole
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12
Q

describe telophase I

A
  • chromosomes reach the opposite pole
  • chromosomes decondense
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13
Q

describe prophase II

A
  • spindle reforms
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14
Q

describe metaphase II

A
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15
Q

describe anaphase II

A
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16
Q

describe telophase II

A
  • spindle disassemble
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17
Q

what is meiosis II

A

identical to mitosis, except there are 2 cells

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18
Q

what are ways in which meiosis increases genetic variation

A
  • crossing over
  • independent/random assortment
  • random fusion of gametes
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19
Q

how does crossing over increase genetic variation

A
  • during prophase I
  • crossing over between non-sister chromatids
  • non-sister chromatids have diff combo of alleles
  • exchange alleles
  • chromatids have new combo of alleles
  • linkage groups broken
  • gametes have unique combo of alleles
  • fusion of gametes
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20
Q

how does random/independent assortment increase genetic variation

A
  • during metaphase I
  • homologous chromosomes randomly align along the equator
  • independent of each other
  • this leads to diff combos of chromosomes in daughter cells
  • results in new combos of alleles
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21
Q

what is random fusion of gametes

A

any male gamete can fuse with any female gamete
- random combination of chromosomes generated

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22
Q

define gene

A

sequence of DNA that codes for a polypeptide

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23
Q

define locus

A

specific position of a gene on the chromosome

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24
Q

define allele

A

a version of a gene

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25
Q

define homozygous & heterozygous

A
  • homozygous = alleles on each homologous pair is same
  • heterozygous = alleles on each homologous pair are different
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26
Q

define dominant & recessive

A
  • dominant = phenotype expressed even if only one is present (heterozygous) + homozygous, it overrides the recessive
  • recessive = phenotype only expressed if homozygous
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27
Q

define codominant

A

both alleles expressed in phenotype

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28
Q

define linkage

A

genes that are close together on the same chromosome
(unlikely to be separated during crossing over)
- GENES ON THE SAME CHROMOSOME

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29
Q

define test cross

A

testing suspected heterozygote w known homozygous recessive

30
Q

define F1 & F2

A

F1 = first generation (of offspring by parents)
= parents homozygous
= F1 heterozygous

F2 = second generation (offspring’s offspring)

31
Q

define phenotype

A

observable features of an organism (eg: brown)

32
Q

define genotype

A

alleles an organism possesses (eg: Bb)

33
Q

define sex-linkage

A

genes found on the X or Y chromosome

34
Q

why is the chi-squared test used ?

A

to test whether the difference between the observed & expected frequencies is significant/ or whether difference is due to chance

35
Q

state the number of phenotypes that each genetic cross produces

A

monohybrid = 2
codominant = 3
multiple alleles = 4

36
Q

state the ratio for heterozygous x homozygous recessive in a dihybrid cross

A

1:1:1:1

37
Q

state the ratio for heterozygous x heterozygous in a dihybrid cross

A

9:3:3:1

38
Q

if the critical value is greater than 0.05, the null hypothesis should be…

A

REJECTED

39
Q

if the critical value is less than 0.05, the null hypothesis should be…

A

ACCEPTED

40
Q

what does the null hypothesis state?

A

there is NO significant difference between the observed & expected results

41
Q

what is the gene, enzyme, type of disease for Albinism

A
  • TYR
  • tyrosinase enzyme
  • autosomal recessive
42
Q

what is the gene, enzyme, type of disease for Huntingtons

A
  • HTT
  • huntingtin
  • autosomal dominant
43
Q

what is the gene, enzyme, type of disease for Sickle cell anaemia

A
  • HBB
  • haemoglobin
  • co-dominant
44
Q

what is the gene, enzyme, type of disease for Haemophilia

A
  • F8
  • factor VIII
  • sex-linked (x linked recessive)
45
Q

symptoms & treatment for albinism

A
  • pale/white skin, hair
  • pink eyes
  • increased susceptibility to sunburn/skin cancer
  • rapid/jerky eye movements
  • poor vision
  • stay in the shade/spf/hat
  • monitor skin
46
Q

symptoms & treatment for Huntington’s

A
  • involuntary movements/uninhibited motor control
  • progressive mental deterioration
  • brain cells lost
  • symptoms come at 30+ –> fatal
  • drugs to control movements (tetrabenazine)
47
Q

symptoms & treatment for Sickle cell anaemia

A
  • haemoglobin less soluble
  • lack of RBCs
  • less oxygen to organs
  • RBC get stuck in capillaries % block blood flow
  • causes pain
  • protection against malaria
  • stem cell transplant
  • blood transfusions
  • medicine
48
Q

symptoms & treatment for Haemophilia

A
  • excessive bleeding
  • large bruises
  • internal bleeding
  • regular injections of clotting factor medicine (curable)
49
Q

differences between structural & regulatory genes

A

structural
- EG: lac z/y/a
- codes for structural protein (eg: amylase)
- needed for structure/function of cell

regulatory
- EG: lac repressor/DELLA repressor
- code for regulatory proteins
- controls gene expression
- codes for transcription factor
- binds to promoters
- allows/stops binding of RNA polymerase

50
Q

differences between repressible & inducible enzymes

A

repressible
- produced continuously
- synthesis can be prevented by binding of repressor protein to specific site
- the thing that codes for this enzyme activates repressor/ allows repressor to bind to operator & stops gene expression

inducible
- synthesis only occurs when substrate present
- transcription of gene only occurs when substrate binds to TF
- eg : lactose permease

51
Q

what are transcription factors

A
  • proteins that bind to DNA
  • bind to promoter
  • allows RNA polymerase/other TFs to bind to promoter/DNA
  • controls gene expression
  • so that genes are expressed at the correct time/order/context/cell type
52
Q

how does gibberellin activate genes

A
  • DELLA proteins inhibit transcription factor
  • gibberellin binds to receptor
  • in aleurone layer
  • DELLA proteins broken down
  • TF binds to promoter region
  • transcription of gene coding for amylase
  • translation
53
Q

how do multiple alleles arise

A
  • gene mutation
  • change in bases by deletion/substitution/insertion
54
Q

what does lacZ code for? & whats its role

A

B-galactosidase / lactase - hydrolyses lactose into glucose + galactose

55
Q

what does lacY code for? & whats its role

A

lactose permease - makes membrane more permeable to lactose

56
Q

Explain why a person who is homozygous recessive for the TYR gene shows albinism [3]

A
  • recessive mutation
  • no melanin
  • pale hair/skin, pink eyes
57
Q

Explain how the lele genotype and its gene product results in dwarf plants [3]

A
  • homozygous recessive
  • lele codes for non-functional enzyme
  • no active gibberellin
  • less cell elongation
58
Q

how DELLA proteins act as repressors preventing gene expression

A
  • bind to transcription factor
  • TF cannot bind to DNA/promoter
  • RNA polymerase cannot bind to promoter
  • no transcription/mRNA not made
59
Q

Using haemophilia as an example, explain the relationship between a gene, a protein and a phenotype [5]

A
  • gene codes for a protein which determines the phenotype
  • F8 gene
  • located on X chromosome (sex-linked)
  • non-functioning factor VIII
  • so excessive bleeding/blood does not clot quickly
  • X^H X ^H = normal female
60
Q

what is gibberellin

A

cell signalling molecule/ hormone

61
Q

what is the role of gibberellin

A
  • cell elongation
  • so plant/stem grows longer
62
Q

suggest explanations for the 9:3:3:1 ratio

A
  • fewer recombinants
  • linked genes/ genes on same chromosome
  • alleles inherited together
  • no independent assortment
  • crossing over produces recombinants
  • during meiosis (prophase I)
63
Q

why do two genes assort independently

A
  • because they are not linked/on separate chromosomes
  • so each homologous pair of chromosomes orients itself separately
  • in metaphase I of meiosis
  • gives 4 new combinations
  • parental allele combinations are not fixed
64
Q

division of the cytoplasm

A

cytokinesis

65
Q

outline the main features of the lac operon

A
  • promoter
  • operator
  • 3 structural proteins (lacY, lacZ, lacA)
66
Q

role of regulatory gene in lac operon

A
  • always expressed
  • controls structural gene expression
  • codes for repressor protein
  • repressor blocks promoter by binding to operator
  • prevents RNA polymerase binding to promoter
  • lactose binds to repressor
  • so repressor cannot bind to operator/ gene expression can occur
67
Q

advantages of repressible enzyme

A
  • made continuously
  • because necessary for cell
  • made until product concentration too high
68
Q

explanations for unexpected results

A
  • mutation
  • crossing over
  • linkage
  • epistasis
  • environmental affects
  • small sample size
69
Q

how does the expression of the TYR gene lead to the production of melanin

A
  • TYR codes for tyrosinase
  • converts tyrosinase to DOPA
  • converts DOPA into dopaquinone
  • dopaquinone converted into melanin

TYR –> tyrosinase –> DOPA –> dopaquinone –> melanin

70
Q

Suggest why structural genes in operons are transcribed together

A
  • share one promoter
  • all proteins work together
71
Q

Explain how a mutation of the TYR gene can result in albinism

A
  • substitution / deletion / insertion
  • change in primary / secondary / tertiary, structure of protein
  • stop codon
  • (so) no / inactive tyrosinase produced
  • tyrosine not converted to DOPA / dopaquinone
  • melanin not formed
72
Q

Explain how a gene mutation can lead to iduronate 2-sulfatase not functioning properly or not
being produced

A
  • base / nucleotide, insertion / deletion / substitution
  • frameshift / changed reading frame
  • stop codon
  • changes / different, primary structure / amino acid sequence
  • changes / different, folding / 3D shape / 3D structure, of enzyme / protein
  • active site does not, bind / fit, substrate / complex molecules

AL Biology (7 decks)

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