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IMMS phase 1 > Genetics > Flashcards

Genetics Flashcards

1
Q

Define genotype.

A

The genetic constitution of an individual.

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2
Q

Define phenotype.

A

The appearance of an individual due to the environment and genetics.

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3
Q

Define allele.

A

An alternative form of a gene at a specific locus.

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4
Q

Summarise autosomal dominant inheritance:

A

Manifests in the heterozygous state (2 different gene alleles on a gene locus)

Both males and females are affected equally.

The disease is present in several generations.

There is a 50% chance of offspring having the disease.

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5
Q

Give an example of an autosomal dominant condition.

A

Huntingtons disease

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6
Q

Summarise autosomal recessive inheritance:

A

Manifests in the homozygous state.

The disease is often not seen in every generation.

25% chance of offspring having the disease.

50% chance of offspring being carriers.

Healthy siblings have a 2/3 chance of being carriers.

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7
Q

Give an example of an autosomal recessive condition.

A

Cystic fibrosis

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8
Q

What is x linked inheritance?

A

A mutated gene on the X chromosome causes the phenotype to always be expressed in males.

Females with the mutated gene on the X chromosome are carriers.

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9
Q

Give an example of an X linked recessive condition.

A

Duchenne muscular dystrophy

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10
Q

What is a mis-sense mutation?

A

A single nucleotide change results in a codon coding for a different amino acid. This can result in a non functional protein or can have no effect (degenerative nature of the genetic code).

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11
Q

What is a non-sense mutation?

A

A single nucleotide change that produces a premature stop codon. This results in an incomplete/non-functional protein.

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12
Q

What is mitosis used for?

A

Growth and repair.

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13
Q

What are the 4 phases of the cell cycle?

A

G1, S, G2 and M

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14
Q

What phases of the cell cycle make up interphase?

A

G1, S and G2

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15
Q

What happens in prophase?

A

Chromatin condenses into chromosomes. Nuclear membrane begins to break down.

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16
Q

What happens in prometaphase?

A

Spindles form. Nuclear membrane completely breaks down.

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17
Q

What happens in metaphase?

A

The chromosomes line up along the midline of the cell. The spindles attach to the centromeres.

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18
Q

What happens in anaphase?

A

The chromosomes are pulled apart and the sister chromatids are pulled towards the nuclear poles.

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19
Q

What happens in telophase?

A

he nuclear membrane reforms and the chromosomes unravel to form chromatin. The spindle fibres disappear.

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20
Q

What happens in cytokinesis?

A

The cytoplasm divides producing 2 genetically identical daughter cells.

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21
Q

How is genetic diversity introduced in meiosis?

A

Metaphase 1 = random assortment.

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22
Q

What is splicing?

A

The removal of introns from pre-mRNA

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23
Q

List 3 features of the genetic code.

A
  1. Non-overlapping
  2. Universal
  3. Degenerate
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24
Q

Define lyonisation.

A

One of the female X chromosomes becomes inactivated early in embryogenesis.

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25
Q

Name 3 molecules that make a nucleotide.

A
  1. Pentose sugar.
  2. Phosphate.
  3. Nitrogenous base.
26
Q

Name 2 places DNA can be found.

A

Cell nucleus DNA
Mitrochondrial DNA

27
Q

What are removed in splicing of pre-mRNA?

A

Introns

28
Q

What is gametogenesis?

A

Precursor cells undergo cell division and differentiation to form haploid gametes.

29
Q

Gametogenesis: when do meiotic divisions occur in a male?

A

At puberty.

30
Q

Gametogenesis: when is meiosis 1 complete in a female?

A

At ovulation.

31
Q

Gametogenesis: when is meiosis 2 complete in a female?

A

If fertilisation occurs.

32
Q

Would an x linked dominant condition be more common in males or females?

A

X linked dominant conditions occur twice as frequently in females as they do in males.

33
Q

Would an X linked recessive condition be more common in males or females?

A

More common in males.

34
Q

Would an affected male of an x-linked recessive condition and an unaffected female have any affected children?

A

No affected children but all the daughters would be carriers.

35
Q

What is multifactorial disease?

A

A disease due to genetic and environmental factors e.g. diabetes or schizophrenia.

36
Q

Define karyotype.

A

The number and appearance of chromosomes in the nucleus of a eukaryotic cell.

37
Q

Define penetrance.

A

The proportion of people with a gene who show the expected phenotype.

38
Q

Define sex limitation.

A

Both sexes have a gene but its expression is limited to only one of the sexes and it is turned off in the other.

39
Q

Define variable expression.

A

Variation in clinical features of a genetic disorder between individuals with the same gene alteration.

40
Q

What is Mendel’s second law?

A

The law of independent assortment. The alleles of one gene sort into gametes independently of the alleles of another gene.

41
Q

A gene sequence is coded in…

A

Single strand DNA.

42
Q

A promoter sequence is coded in …

A

Single strand DNA.

43
Q

What is a promoter sequence?

A

The promoter region controls when and where the RNA polymerase will attach to DNA so transcription can commence.

44
Q

What is a transcriptome?

A

All the messenger RNA molecules in a cell.

45
Q

How many genes are there in the human genome?

A

20,000

46
Q

What is it called when a child shows a phenotype for a disease younger than their father/mother does? e.g. in huntington’s disease.

A

Anticipation

47
Q

What are Mendel’s 3 laws?

A
  1. Law of dominance.
  2. Law of independent assortment.
  3. Law of segregation.
48
Q

How many hydrogen bonds form between adenine and thymine?

A

2

49
Q

How many hydrogen bonds form between cytosine and guanine?

A

3

50
Q

What type of inheritance pattern is seen with sickle cell disease?

A

Autosomal recessive

51
Q

What is a single nucleotide polymorphism?

A

A single nucleotide substitution in DNA resulting in variation amongst a population.

52
Q

Which phase of mitosis is this: The chromosomes are moving towards opposite poles of the cell and there are no nuclear membranes.

A

Anaphase

53
Q

What is non-disjunction?

A

The failure of chromatids to separate.

54
Q

What are the 4 bases in RNA?

A

Adenine, Cytosine, Guanine, Uracil.

55
Q

Briefly describe translation.

A

A tRNA with a complementary anticodon to the codon on mRNA binds. Peptide bonds from between amino acids = polypeptide chain.

56
Q

Where does translation occur?

A

Ribosome

57
Q

What is the product of transcription?

A

mRNA

58
Q

In what direction does DNA polymerase read?

A

3’ to 5’ (but replication occurs in the 5’ to 3’ direction).

59
Q

What is the function of topoisomerase?

A

It unwinds the DNA double helix by relieving the supercoils.

60
Q

What is gonadal mosaicism?

A

When there are 2 different populations of cells in the gonads. One population is normal and the other is mutated. All gametes from the mutated line are effected

61
Q

What condition is trisomy 21?

A

Down’s syndrome

62
Q

What causes trisomy 21?

A

Failure of the chromatids to separate; non-dysjunction.

IMMS phase 1 (9 decks)

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