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Flashcards in Genetics Deck (38)
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1

In which direction is DNA always replicated?

5' to 3' carbon

2

How is DNA packaged?

It is wrapped around positively charged histone proteins

Amongst other proteins, DNA is then wound into chromosomes

3

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

30,000

4

What are the 5 phases of the cell cycle?

  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

5

Which protein can detect and attempt repair of DNA damage?

p53

6

Under which circumstances may p53 halt G2?

Low oxygen concentrations

7

What is Li-Fraumeni syndrome?

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

8

What are the 5 different phases of meiosis I?

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

9

What are the three differences between RNA and DNA?

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

10

After transcription what is produced?

Pre-mRNA

11

How is mature mRNA obtained?

Splicing of introns to leave only exons which contain coding DNA

12

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

G0

13

Which enzyme is responsible for unzipping DNA?

DNA helicase

14

Which enzyme copies the 5'-3' strand?

DNA polymerase

15

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

DNA ligase

16

How is variation obtained in meiosis?

  • Crossing over
  • Independent assortment

17

What is a polymorphism?

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

18

What is a mutation?

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

19

How do polymorphisms and mutations differ?

  • Polymorphisms are functioning versions of genes
  • Mutations can be harmful

20

What is a missense mutation?

A wrong base is used in one of the codons

21

What is karyotyping?

It looks at chromosomes as a whole

Can see deletions of >5 million base pairings

 

22

What is a balanced translocation?

There is an even exchange of material between chromosomes

There is no missing or extra genetic information

Usually such chromosomes will still function

23

What is an unbalanced translocation?

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

What are acrocentric chromosomes?

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

What is fluorescent in-situ hybridisation?

FISH

Chromosomes can be labelled by fluorescent probes

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

26

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

25%

27

What does the term penetrance mean?

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

28

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

It is a random process

29

What is multifactorial disease?

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

30

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

Low