Topic 2C : Inheritance

Question 1

gene

Answer 1

sequence of based on a DNA molecule that codes for a sequence of amino acids in a polypeptide

Question 2

allele

Answer 2

a different version of a gene

Question 3

genotype

Answer 3

the alleles a person has

Question 4

phenotype

Answer 4

the characteristic displayed by an organism

Question 5

incomplete dominance

Answer 5

when trait from a dominant allele isn’t completely shown over the trait produced by the recessive allele so both alleles influence the phenotype

Question 6

monohybrid inheritance

Answer 6

inheritance of single characteristic controlled by different alleles

Question 7

what allele causes cystic fibrosis

Answer 7

recessive

Question 8

explain what happens in people with cystic fibrosis

Question 9

explain how cystic fibrosis affect the respiratory system

Answer 9

cilia unable to move mucus towards the throat as its sticky and thick so mucus builds up in the airways

airways become blocked by mucus so gas exchange cant happen below the blockage

surface area for gas exchange reduced causing breathing difficulties

Question 10

explain how cystic fibrosis affects the digestive system

Answer 10

mucus blocks tube connecting pancreas to small intestine preventing digestive enzymes produced by the pancreas from reaching the small intestine

mucus causes cysts to form in pancreas which inhibit the production of enzymes which reduces the ability to digest food and absorb nutrients

mucus lining the small intestine is abnormally thick and inhibits the absorption of nutrients

Question 11

explain how cystic fibrosis affects the reproductive system

Answer 11

tubes connecting the testicles to penis are absent and can become blocked in others so sperm produced cant reach the penis

thickened cervical mucus prevents sperm reaching the egg so sperm has to travel through thick mucus to reach the egg which reduces its motility and its chances of making it to the egg

Question 12

what causes a change in the function of the CFTR protein

Answer 12

mutation in the sequence of amino acids coding for the protein

Question 13

explain how a disfunction in the CFTR protein causes thick mucus

Answer 13

chloride ions cant leave the cell and enter the mucus through the CFTR protein channel

sodium ions dont move into the mucus and therefore water moves out of the mucus into the cell by osmosis

Question 14

describe the role of the CTR protein in enduring that the mucus produced in the lungs has the right consistency

Answer 14

chloride ions leave cells through CFTR chanell protein into mucus

sofiym ions follow the chloride ions increasing the solute concentration in the mucus

water moves out of the cells by osmosis into the mucus

Question 15

what are the types of errors that could occur during DNA replication

Answer 15

substitution

deletion

insertion

duplication

inversion

Question 16

substitution

Answer 16

one bade is substituted for another

Question 17

deletion

Answer 17

base is deleted

Question 18

insertion

Answer 18

extra base is added

Question 19

duplication

Answer 19

one or more bases are repeated

Question 20

inversion

Answer 20

sequence of bases is reversed

Question 21

what are the different methods of DNA replication

Answer 21

semi-conservative

conservative

Question 22

conservative method

Answer 22

original DNA strands stay together and new DNA molecules contain two new strands

Question 23

explain the whole process of Messelson and Stahls experiment

Answer 23

bacteria was grown in a nutrient broth containing light nitrogen and one in a broth containing heavy nitrogen. as bacteria reproduced, it took up the nitrogen from the broth to help make nucleotides for new DNA

sample of DNA was taken from each batch of bacteria and spun in a centrifuge where DNA from heavy nitrogen bacteria settles lower down the tube because its heavier

bacteria grown in heavy nitrogen broth was taken and put in a broth containing only light nitrogen. bacteria left for a round of replication and spun in the centrifuge

Question 24

what was the results of the semi conservative experiment

Answer 24

new bacterial DNA molecules contained one strand of old DNA containing heavy nitrogen and one strand of new DNA containing light nitrogen

DNA settled between where light nitrogen DNA settled out and where the heavy nitrogen DNA settled out

Question 25

explain the process of DNA replication

Answer 25

DNA helicase breaks H bonds between bases on the two polynucleotide DNA strand making the helix unwind forming two single strands.

each original strand acts as a templare for a new strand and complementary bade pairing occurs between free DNA nucleotides and the bases on the strands

condensation reaction joins nucleotides of the new strands together catalysed by DNA polymerase

hydrogen bonds form again so that each new DNA molecule contains one strand from the original DNA molecule and one new strand

Question 26

preimplantation genetic diagnosis

Answer 26

screening embryos produced by IVF for genetic disorders before implanted into the woman

Question 27

state two benefits of preimplantation genetic diagnosis

Answer 27

reduces the chances of having a baby with a genetic disorder

avoid abortion

Question 28

social and ethical issues of PGD

Answer 28

can be used to find out other characteristics leading to concerns that in the future embryos may be selected for other characteristics

false results provide incorrect information

Question 29

name the two prenatal tests

Answer 29

amniocentesis and chorionic villus sampling

Question 30

when is chorionic villus sampling carried out

Answer 30

11-14 weeks

Question 31

when is amniocentesis carried out

Answer 31

15–20 weeks

Question 32

chorionic villus sampling

Answer 32

sample of cells taken from placenta containing fetal DNA that could be analysed

done via the abdomen using a fine needle or the vagina using a catheter

initial results available but more in depth can take two or more weeks to arrive

Question 33

risk of miscarriage of CVS

Answer 33

1-2%

Question 34

amniocentesis

Answer 34

sample of cells taken from amniotic fluid using a fine needle via the abdomen

cells contain foetal cells which contain DNA that can be analysed

results not available until 2-3 weeks after but rapid test with less info available in 3-4 days

Question 35

risk of miscarriage of amniocentesis

Answer 35

1%

Question 36

carrier testing

Answer 36

offered to individuals with family history of genetic disorders and shows whether people without a disorder carry an allele that can cause a disorder

Question 37

social and ethical issues of carrier testing

Answer 37

emotional stress

not 100% accurate

other disorders could be found

insurance companies or employers could used the results (genetic discrimination)