Genetics

Question 1

what are the 2 sex chromosomes women have?

Answer 1

2x X chromosomes.

Question 2

what are the 2 sex chromosomes men have?

Answer 2

X and Y chromosome.

Question 3

what are the 3 components of DNA?

Answer 3

• phosphate
• sugar
• nitrogenous base

Question 4

what does adenine bond with?

Answer 4

guanine

Question 5

what does cytosine bond with?

Answer 5

thymine / uracil.

Question 6

what is meant by the term frameshift mutation?

Answer 6

insertion or deletion of a number of bases not divisible by 3.

Question 7

what happens if there is a loss or a gain of nucleotides in DNA?

Answer 7

frame shift in reading the genetic code

Question 8

what is meant by the term silent mutation?

Answer 8

change in the nucleotide sequence but not the amino acid it is code for.

Question 9

what is meant by the term missense mutation?

Answer 9

change the nucleotide sequence such that a different amino acid is encoded.

Question 10

what is meant by the term nonsense mutation?

Answer 10

change the coding sequence to a stop codon, resulting in truncated proteins.

Question 11

what enzyme can detect and remove an error in DNA replication?

Answer 11

exonuclease.

Question 12

what are 2 examples of external physical causes for mutations in genetics?

Answer 12

• ionising radiation (x-rays) causing strand breaks, sugar or base destruction.
• non-ionising radiation (UV-light) causes new chemical bonds to form.

Question 13

what are 2 examples of external chemical causes for mutations in genetics?

Answer 13

• base analogues
• nitrous acid (changes cylosine to uracil)
• alkylating agents (causes lesions that result in error prone repair)

Question 14

what is meant by the term allele?

Answer 14

different forms (eg DNA sequence) of the same gene

Question 15

what is meant by the term genotype?

Answer 15

the genetic components.

Question 16

what is meant by the term phenotype?

Answer 16

the visible appearance.

Question 17

what is meant by the term diploid?

Answer 17

organisms with 2 copies of each chromosome.

Question 18

what are 3 examples of autosomal recessive disorders ?

Answer 18

• Cystic fibrosis
• Sickle-cell anaemia
• Dentinogenesis imperfects

Question 19

what is meant by the term autosomal recessive?

Answer 19

the condition is recessive so an individual would need to have the disorder on both chromosomes to have the disorder.

Question 20

what is meant by the term autosomal dominant ?

Answer 20

the condition is dominant so an individual would need to have the disorder on only one chromosomes to have the disorder.

Question 21

what are the effects on the body of cystic fibrosis?

Answer 21

CFTR controls export of chloride ions in the epithelial cells of the airways. so cystic fibrosis would cause build-up of sticky mucus in the airways where bacterial pathogens can invade and lead to disease.

Question 22

what effect does sickle-cell anaemia have on the body?

Answer 22

single base mutations affects how the B globing molecules form the structure that carries O2 around the body.

Question 23

why in some areas of the world can having once chromosome with sickle-cell anaemia increase life expectance?

Answer 23

in areas where malaria is an epidemic.

Question 24

how does Dentinogenesis imperfects effect the body?

Answer 24

effects the formation of dentine on the teeth due to a C to T substitute in the DSPP gene.

Question 25

what is an example of an autosomal dominant disorder?

Answer 25

Huntington’s diseases

Question 26

how does Huntington’s disease effect the body?

Answer 26

• increases in the number of repeated of the triple sequence CAG. - the more copies the worse the effects.
• causes depression, dementia and involuntary spasms.

Question 27

what are 3 examples of X-linked inheritance disorders?

Answer 27

• haemophilia
• amelogenesis imperfecta
• lionisation/ x-inactivation.

Question 28

what happens if you have X-inactivation and are a carrier of a recessive condition?

Answer 28

effects of the defective gene become visible and have an effect eg amelogenesis imperfects - you will have stripy teeth where some areas are effected and others are not.

Question 29

what are 2 examples of multi-factorial genetic disorders in the oral cavity?

Answer 29

• oral cancer

- per disease

Question 30

why is oral cancer classed as a multi-factorial genetic disorder?

Answer 30

genetics can make people more susceptible but lifestyle can increase probability and/or speed up the disease.

Question 31

why is periodontal disease classed as a multi-factorial genetic disorder?

Answer 31

even with good OH it can still be developed due to an altered response to infection increasing the severity of the condition.

Question 32

How is plasmid and gene cloning carried out?

Answer 32

• target gene is inserted into DNA where it comes plasmid.
• plasmid introduced into bacteria and is selected using anti-bodies.
• bacteria makes more plasmid DNA called vectors
• vector and DNA digested in same enzymes join together by DNA ligase resulting in recombination DNA can be introduced into the cell and make them permeable.

Question 33

what are the stages of southern blotting?

Answer 33

1- digested DNA with appropriate restriction enzymes.
2- denture DNA to make single strands and transfer to nitrocellulose membrane
3- hybridise DNA with specific probe
4 - defect DNA fragment

Question 34

what is the purpose of southern blotting?

Answer 34

allows for visualisation of specific DNA fragment.

Question 35

what can genetic testing be used for?

Answer 35

• pre-natal screening

- risk assessment

Question 36

what are the benefits of genetic testing?

Answer 36

• personalised medications
• adverse drug reactions
• genetic predictions
• identify risk groups

Question 37

what are the disadvantages of genetic testing?

Answer 37

• expense
• misuse of data
• creating stigmatisation
• lead to selection of favoured gene so loss of diversity.