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Principles > Genetics > Flashcards

Genetics Flashcards

1
Q

Each human has how many pairs of chromosomes?

A

23 pairs in total

22 autosomal pairs, 1 sex-linked pair

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2
Q

G0 phase of the cell cycle

A

Most cells are resting, carrying out their normal function

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3
Q

G1 phase of the cell cycle

A

1st growth phase as chromosomes become ready to be replicated

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4
Q

S phase of the cell cycle

A

DNA replication occurs

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5
Q

G2 phase of the cell cycle

A

2nd growth phase involving proteins etc.

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6
Q

M phase of the cell cycle

A

Mitosis - mechanical separation of cell into two daughter cells
Two daughter cells are identical, diploid cells

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7
Q

Variation occurs during meiosis by two main methods, which are?

A

Crossing over

Independent segregation of homologous chromosomes

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8
Q

In meiosis, one diploid cell becomes…

A

Four haploid daughter cells

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9
Q

Examples of sequence variations between genes?

A

Single nucleotide polymorphisms (SNPs)

Deletions/duplications

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10
Q

A polymorphism is…

A

A change in the genome that does not cause disease in its own right, but can predispose to a common disease

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11
Q

Chromosome 22 looks like a…

A

Teddy bear

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12
Q

A chromosome consists of…

A

Telomeres at each end
Short arm (p)
Centromere
Long arm (q)

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13
Q

A chromosome is metacentric if…

A

Both arms are roughly the same length

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14
Q

A chromosome is acrocentric if…

A

The p (short) arm is so short it is hard to observe

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15
Q

A chromosome is telocentric if…

A

The centromere is located at the terminal end of the chromosome

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16
Q

An aneuploidy is…

A

An abnormal number of chromosomes
Monosomy - missing chromosome from one pair
Trisomy - extra chromosome in a pair

17
Q

Reciprocal translocations are when…

A

Segments from two different chromosomes have been exchanged

18
Q

Robertsonian translocations are when…

A

A chromosome attaches to another chromosome at the centromere
Only occurs with 13, 14, 15, 21, 22

19
Q

Monosomy of the sex chromosomes causes…

A

Turner’s syndrome

20
Q

Trisomy of chromosome 21 causes…

A

Down’s syndrome

21
Q

What is FISH?

A

DNA probes specifically bind to areas of individual chromosomes and apply a fluorescein stain to make the chromosome visible
Useful for detecting aneuploidies

22
Q

Penetrance is defined as…

A

The likelihood of having the disease given you have the genetic mutation

23
Q

Mendelian inheritance encompasses which disorders?

A

Autosomal dominant
Autosomal recessive
X-linked
Mitochondrial

24
Q

Autosomal dominant disease occurs when…

A

There is one faulty copy of the gene
Seen in all generations
50% risk of affected child if parent affected

25
Q

Autosomal recessive disease occurs when…

A

There are 2 faulty copies of the gene
Often only one generation affected
25% risk of affected child if parents are carriers
Increased likelihood if parents are related

26
Q

X-linked disease occurs when…

A

The disease is carried on the X-chromosome only
50% of male children of a female carrier affected
50% of female children of a female carrier affected
All male children of a male carrier normal
All female children of a male carrier will be carriers

27
Q

Mitochondrial disease occurs when…

A

Diseased mitochondria passed from mother to child

28
Q

What is mosaicism?

A

Occurs when cells within the same person have a different genetic makeup

29
Q

Epigenetic variation describes…

A

Functional modifications to the genome that do not involve a change in the nucleotide sequence

30
Q

Methylation inhibits which process?

A

DNA transcription

31
Q

What is imprinting?

A

Variation in gene expression depending on which parent you inherit the gene from
e.g. in Angelman’s syndrome, mother’s UBE3A works fine but father’s is methylated

32
Q

Heteroplasmy is when…

A

Different daughter cells contain different proportions of mutant mitochondria (similar to mosaicism)

33
Q

Where are the 2 checkpoints in the cell cycle where DNA can acquire mutations?

A

Between G2 and M

Between G1 and S

34
Q

What is the function of oncogenes?

A

Promote cell division

35
Q

What is the function of tumour suppressors?

A

Inhibit cell division

36
Q

Only one copy of the tumour suppressor gene is required to be mutated for cancer to occur. True/False?

A

False

2 copies required

37
Q

Cancer is most often inherited as a high penetrance Mendelian disorder. True/False?

A

False

More usually multifactorial

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