Genetics

Question 1

Describe double helix

Answer 1

A spiral molecule made of 2 strands of DNA joined by bases. Contains the genetic information in a linear sequence of chemical subunits called nucleotides

Question 2

What are 4 bases in DNA?

Answer 2

Adenine
Thymine
Guanine
Cytosine

Question 3

What is DNA?

Answer 3

Deoxyribonucleic acid. 2 strands of nucleic acids on sugar phosphate backbone formed in double helix.

Question 4

What is a chromosome?

Answer 4

Strand of DNA and protein. The DNA and histones make up nucleosomes. The nucleic acid and histones are known and chromatin. The chromosome is almost 5cm long so it twists and twists and twist to form recognisable X shape.

Question 5

What is a gene?

Answer 5

Section of DNA containing particular set of instructions related to bodily function

Question 6

How do bases join together?

Answer 6

A-T for example join together by hydrogen/polar bonding (a weak bond)

Question 7

How do bases join to the deoxyribose strands?

Answer 7

covalent bonds

Question 8

What are 4 bases in RNA?

Answer 8

Adenine
Cytosine
Guanine
Uracil (instead of thymine)

Question 9

Describe how DNA becomes protein

Answer 9

DNA - transcription - mRNA - travels out of nucleus and attaches to ribosome - translation in groups of 3. t RNA bring along the amino acid which forms string to make protein.

Question 10

What are codon and anti-codon?

Answer 10

codon = mRNA
anti-codon = tRNA

Question 11

How many chromosomes in each cell?

Answer 11

23 pairs = 46 in total

Question 12

What are stages of mitosis

Answer 12

Prophase
Metaphase
Anaphase
Telophase

Question 13

Describe mitosis cycle

Answer 13

Prophase - DNA organises and condenses into chromosome shape. Nucleolus disappears. Centrosomes start to form microtubules

Pro Metaphase - nuclear membrane breaks down. Microtubules attach to kinetocre

Metaphase - chromatids align along the middle

Anaphase - Microtubules shorten, pulling chromatids apart

Telophase - Now have 46 chromatids at each pole. Microtubules break down. Nuclear membrane forms at each end. Chromosomes uncoil into uncondensed state

Cytokinesis - division of cell

Question 14

Describe interphase

Answer 14

G1 - growth phase
Cell performs functions and duplicates organelles
S - synthesis - duplicates DNA
G2 - grow to final size

Question 15

What does meiosis produce?

Answer 15

Gametes - haploid cells. (23 single chromosomes)

Question 16

What is process where genetic information is changed?

Answer 16

Crossing over during prophase I or called recombination

Question 17

What makes up chromosomes?

Answer 17

DNA and histones (protein). 2 chromatids with centromere in the middle = chromosome

Question 18

What are autosomes?

Answer 18

All pairs of chromosomes that are not sex chromosomes

Question 19

What is an allele?

Answer 19

The small section of chromosome that codes specific gene

Question 20

What is autosomal dominant inheritance?

Answer 20

Abnormal gene on one of the non-sex chromosomes.

Males and Females express the allele and transmitted equally to sons and daughters.

Ratio of affected to unaffected children = almost always 1:1

50% chance of each child being effected

Every affected person has an affected parent

Question 21

What are x-linked disorders?

Answer 21

Abnormal gene on X

Question 22

Who is usually affected by X linked disorders?

Answer 22

Males

Question 23

Give 4 examples of X-linked disorder

Answer 23

Duchennes MD
Haemophlia
Colour blindness
Fragile X

Question 24

Give 4 examples of autosomal recessive disorder

Answer 24

CF
Sickle Cell
Thalasemia
Tay-Sachs

Question 25

Give 2 examples of autosomal dominant disorder

Answer 25

Neurofibromatosis | Tuberus sclerosis

Question 26

What is difference between phenotype and genotype?

Answer 26

``` Genotype = genetic code Phenotype = physical characteristics ```

Question 27

Describe RNA

Answer 27

Determines the amino acid composition of proteins, which in turns determines the function of the protein and therefore the function of that particular cell

Question 28

Describe an amino acid

Answer 28

A simple organic compound containing a carboxyl and an amino group

Question 29

What is difference between dominant and recessive gene?

Answer 29

Dominant gene exerts its effect when present on only one chromosome Recessive gene has to be present on both chromosomes in order to manifest itself.

Question 30

What is autosomal Recessive inheritance?

Answer 30

2 copies of abnormal gene must be present Children usuallyy affected but not the parents 1:4 chance of each pregnancy being affected Some carriers can express variations in genetic disease expression

Question 31

What are x-linked disorders?

Answer 31

Mother a carrier Usually unaffected Female carriers - X chromosomal dominance cancels out the affected other X chromosomes

Question 32

Name 4 syndromes are chromosome related?

Answer 32

Trisomy 21 Turners Syndrome Edwards Syndrome Kleinfelters Snydrome

Question 33

What happens in prophase of mitosis?

Answer 33

Nucleolus disappears DNA starts to condense and form characteristic X shaped chromosomes Centrosomes start making tubules

Question 34

What happens in pro metaphase of mitosis?

Answer 34

Nuclear membrane breaks down Microtubules grow and attach to kineticore on each chromatid.

Question 35

What happens in metaphase of mitosis?

Answer 35

Chromosomes align along middle of cell

Question 36

What happens in anaphase of mitosis?

Answer 36

Microtubule fibres start to shorten - pulling chromatids apart to either end of the cell.

Question 37

What happens in telophase of mitosis?

Answer 37

Microtubules break down Nuclear membrane forms around each set of chromosomes (23 pairs) Chromosomes uncondense and go into uncoiled state. Then cytokinesis where the cell divides.

Question 38

What happens in interphase of mitosis cell cycle?

Answer 38

G1 - growth stage. Cell grows and performs functions. Duplicates organelles S - synthesis. DNA is duplicated. G2 - growth stage to final size

Question 39

What happens in prophase I of meiosis?

Answer 39

DNA condenses 2 pairs of sister chromatids align and have recombination of genetic material 'crossing over' Centrosomes head to poles and start making microtubules nuclear membrane breaks down

Question 40

What happens in metaphase I of meiosis?

Answer 40

Chromosomes align along equator in random order (hence different combinations of genetic material in gametes)

Question 41

What happens in anaphase I of meiosis?

Answer 41

Microtubules shorten and pull chromatids apart. Sister chromatids remain attached.

Question 42

What happens in telophase I of meiosis?

Answer 42

Cell separates into 2 cells.