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
Autosomal recessive disease occurs when...
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
X-linked disease occurs when...
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
Mitochondrial disease occurs when...
Diseased mitochondria passed from mother to child
28
What is mosaicism?
Occurs when cells within the same person have a different genetic makeup
29
Epigenetic variation describes...
Functional modifications to the genome that do not involve a change in the nucleotide sequence
30
Methylation inhibits which process?
DNA transcription
31
What is imprinting?
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
Heteroplasmy is when...
Different daughter cells contain different proportions of mutant mitochondria (similar to mosaicism)
33
Where are the 2 checkpoints in the cell cycle where DNA can acquire mutations?
Between G2 and M | Between G1 and S
34
What is the function of oncogenes?
Promote cell division
35
What is the function of tumour suppressors?
Inhibit cell division
36
Only one copy of the tumour suppressor gene is required to be mutated for cancer to occur. True/False?
False | 2 copies required
37
Cancer is most often inherited as a high penetrance Mendelian disorder. True/False?
False | More usually multifactorial