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Principles > Genetics > Flashcards

Genetics Flashcards

1
Q

In which direction is DNA always replicated?

A

5’ to 3’ carbon

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2
Q

How is DNA packaged?

A

It is wrapped around positively charged histone proteins

Amongst other proteins, DNA is then wound into chromosomes

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3
Q

How many genes are available to be coded in the body?

A

30,000

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4
Q

What are the 5 phases of the cell cycle?

A
  1. G1 - Cell growth
  2. G0 - Cell functions normally and does not replicate
  3. S - DNA synthesis and replication
  4. G2 - DNA replication is checked
  5. M - Mitosis occurs
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5
Q

Which protein can detect and attempt repair of DNA damage?

A

p53

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6
Q

Under which circumstances may p53 halt G2?

A

Low oxygen concentrations

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7
Q

What is Li-Fraumeni syndrome?

A

A condition characterised by a mutation in the tp53 gene resulting in defective p53 protein

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8
Q

What are the 5 different phases of meiosis I?

A
  1. Interphase
  2. Prophase
  3. Metaphase
  4. Anaphase
  5. Telephase (and cytokinesis)
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9
Q

What are the three differences between RNA and DNA?

A
  1. RNA is single stranded
  2. RNA uses ribose rather than deoxyribose sugar in DNA
  3. Uracil is used in RNA rather than thymine
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10
Q

After transcription what is produced?

A

Pre-mRNA

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11
Q

How is mature mRNA obtained?

A

Splicing of introns to leave only exons which contain coding DNA

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12
Q

In terms of the cell cycle, which stage will the cell remain in most of its life?

A

G0

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13
Q

Which enzyme is responsible for unzipping DNA?

A

DNA helicase

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14
Q

Which enzyme copies the 5’-3’ strand?

A

DNA polymerase

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15
Q

Okazaki fragments are utilised to copy the 3’-5’ strand, these are joined with the aid of which enzyme?

A

DNA ligase

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16
Q

How is variation obtained in meiosis?

A
  • Crossing over
  • Independent assortment
17
Q

What is a polymorphism?

A

DNA variant which has a population frequency of greater than 1%

18
Q

What is a mutation?

A

A DNA variant which causes or predisposes to a specific disease?

19
Q

How do polymorphisms and mutations differ?

A
  • Polymorphisms are functioning versions of genes
  • Mutations can be harmful
20
Q

What is a missense mutation?

A

A wrong base is used in one of the codons

21
Q

What is karyotyping?

A

It looks at chromosomes as a whole

Can see deletions of >5 million base pairings

22
Q

What is a balanced translocation?

A

There is an even exchange of material between chromosomes

There is no missing or extra genetic information

Usually such chromosomes will still function

23
Q

What is an unbalanced translocation?

A

There is an unequal exchange of genetic material between chromosomes

This results in extra or missing information

Usually these chromsomes do not function correctly

24
Q

What are acrocentric chromosomes?

A

A chromosome in which the centromere is located very near the end of the chromosome

Two acrocentric chromosomes may stick together is very bad

25
Q

What is fluorescent in-situ hybridisation?

A

FISH

Chromosomes can be labelled by fluorescent probes

This can aid in identifying aneuploidy (too many chromosomes in a cell) or translocations etc

26
Q

What is the risk of a carrier mother passing on a sex-linked genetic condition to her son?

A

25%

27
Q

What does the term penetrance mean?

A

The extent to which a particular gene is expressed in the phenotype of the individual carrying it

28
Q

In females how is it decided which X chromosome undergoes X inactivation?

A

It is a random process

29
Q

What is multifactorial disease?

A

Disease in which mutations in multiple genes combine with environmental factors to cause disease

30
Q

Genes involved in multifactorial disease will have what level of penetrance?

A

Low

31
Q

What do DNA methylation and acetylation affect about the DNA and histone binding?

A

They increase the strength of binding

This may slow the rate of transcription when excessive and may cause disease

32
Q

Describe the meaning of imprinting

A

Differences in gene expression depending on whether a gene is maternally or paternally inherited

33
Q

Mitochondrial DNA is inherited from where?

A

Almost entirely the mother

34
Q

What is mosaicism?

A

The presence of two or more populations of cells with different genotypes in one individual

35
Q

What are the two types of mosaicism?

A
  1. Somatic - derived from a post-zygotic mutation
  2. Gonadal - a person has two populations of cells in the gonads, one with a DNA mutation or chrmosome anomaly
36
Q

BRCA1/2 mutations are associated with what?

A

Increased lifetime risk of breast or ovarian cancer

(BRCA1/2 are associated with DNA repair)

37
Q

What is the normal function of the CFTR gene?

A

It functions as a channel across the membrane that produces mucus, sweat, saliva, tears and digestive enzymes

It transports cholride ions out of the cell which indirectly controls the water movement allowing for thin free flowing mucus

38
Q

Mutations in CFTR cause what?

A

Sodium is not pumped out the cell and into the lumen or digestive or respiratory passages so mucus is thick as water does not enter these areas

Principles (10 decks)

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