23 Patterns of Inheritance Flashcards

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1
Q

what is a monogenetic trait?

A

a characteristic controlled by a single trait

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2
Q

how does a mutation in the CFTR gene on chromosome 7 cause cystic fibrosis?

A

gene codes for transporter protein that allows Cl- ions to pass out of alveolar cells

the mutation cause non-functionality of the protein

Cl- ions cannot move out of the cell ∴ no water is drawn out by osmosis ∴ surfactant mucus remains thick

ciliated epithelium cannot move it ∴ it accumulates ∴ bacteria are trapped –> infection

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3
Q

what are the three types of substitution mutations to the genetic code?

A

silent = same nucleotide/amino acid exchanged

missense = disruption of tertiary structure of protein

nonsense = early stop codon ∴ shortens polypeptide chain

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4
Q

what is PKU?

A

{phenylketonuria}

mutation prevents formation of enzyme required to breakdown phenylalanine

∴ phenylalanine accumulates in blood/tissue fluid –> brain damage

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5
Q

what is Huntington’s disease?

A

accumulation of protein fragments in brain neurones, reducing ability to talk, walk and think

due to an insertion mutation on chromosome 4 - CAG repeated 40+ times

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6
Q

what is sickle anaemia?

A

a substitution in the gene which codes for the β polypeptide chain in haemoglobin

valine replaces glutamate

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7
Q

what is codominance?

A

two or more alleles that do not show complete dominance, resulting in an intermediate condition of the phenotype

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8
Q

what is the function of HLAs?

A

to help the immune system distinguish the body’s own proteins from proteins made by pathogens

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9
Q

what do HLA-A, -B and -C do?

A

produce proteins present on cell surfaces

if from ingesting a foreign body, causes an immune response and the cell to self-destruct

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10
Q

what is a chromosome mutation?

A

a random change in the number of chromosomes or chromosome structure, usually following an error in mitosis

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11
Q

what is sex-linkage?

A

inheritance of genes on the X and Y chromosomes

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12
Q

what is haemophilia A?

A

a sex-linked genetic disorder where clotting factor VIII is not produced, causing an increase in clotting time

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13
Q

what is translocation?

A

a piece of chromosome breaks off and is transferred to another chromosome

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14
Q

what is non-disjunction?

A

a change in the diploid number of chromosomes

when homologous chromosomes don’t separate in meiosis I/sister chromatids don’t separate in meiosis II

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15
Q

what is Turner’s syndrome?

A

non-disjunction during oogenesis causes one oocyte to be XX, the other is OO

resulting zygote is XO and has 45 chromosome (2n-1)

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16
Q

what is Klinefelter’s syndrome?

A

non-disjunction during spermatogenesis causes one sperm to be XY, the other is OO

resulting zygote is XXY

17
Q

what are the three main genetic tests?

A

parental carrier testing

prenatal

newborn screening

18
Q

what is pedigree analysis?

A

a method of predicting the likelihood of a child being born with a genetic disorder

19
Q

what is the role of a genetic counsellor?

A

to help people understand the risks of children inheriting diseases, and make informed decisions

20
Q

when is genetic counselling offered?

A

known genetic condition

history of cancer

both parents have a disease-causing allele

parents have previously lost a baby during pregnancy/infancy

21
Q

what are the ethical issues with genetic counselling?

A

parents have to make a difficult decision

counsellors can learn secretive information

22
Q

what is a dihybrid cross?

A

a cross between two F(1) offspring of two individuals which have different characteristics

23
Q

what are dihybrid crosses used for?

A

to calculate and predict genotype/phenotype ratio of offspring involving unlinked autosomal genes

usually results in a 9:3:3:1 ratio of characteristics