Inheritance(topic 2)

Question 1

How does Dna replication occur

Answer 1

The enzyme dna helicase breaks the hydrogen bonds between the two polynucleotide dna strands.this makes the helix unwind to make two single strands

Each original strand acts as a template for a new strand

A complementary base pairing will attach to the original strand

Condensation reactions join the nucleotides to the new strands catalyses by th enzyme DNA polymerase

Hydrogen bonds form between the bases on the original and new strands

Each new Dna molecule contains one strand from the original DNA molecule

Question 2

What is a gene

Answer 2

A sequence of bases on a dna molecule that codes for a protein which results in a characteristic

Question 3

What is a allele

Answer 3

A different version of a gen

Question 4

What is a genotype

Answer 4

The alleles a person has

Question 5

What is a phenotype

Answer 5

The characteristics displayed by a organism

Question 6

What does dominant mean

Answer 6

An allele whose characteristic appears in the phenotype even when there is only one copy

Question 7

What does recessive mean

Answer 7

An allele whose characteristic will only appear in the phenotype of two copies are present

Question 8

What does the term incomplete dominance mean

Answer 8

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

Question 9

What is a homozygote

Answer 9

An organism that carries two copies of the same allele for a certain characteristic

Question 10

What is a heterozygote

Answer 10

An organism that carries two different alleles for a certain characteristic

Question 11

What a mutations

Answer 11

Changes in the sequence of DNA

Question 12

What is cystic vibrosis

Answer 12

A mutation in the gene which codes for the CFTR protein

Question 13

How do cystic vibrosis affect the the respiratory system

Answer 13

Cillia are unable to move the mucus towards the throat because it’s so thick and sticky

This means that mucus builds up the airways

So has exchange can’t take place below the blockage

Surface area for gaseous exchange is reduced causing breathing difficulties

People with cystic vibrosis more likely to get lung infections as microorganism can’t be removed

Question 14

How does cystic vibrosis affect the reproductive system

Answer 14

Prevent sperm reaching the penis

Reduces the mobility of the sperm

Question 15

How can cystic vibrosis affect the digestive system

Answer 15

Excess mucus build up cysts to grow on the pancreas which inhibits the production of the enzymes and reduces ability to digest food and absorb nutrients

Question 16

Why is the mucus sticky for people with cystic vibrosis

Answer 16

Mutation in the protein is less efficient at transporting chloride ions out of a cell so less water moves out by osmosis .

Question 17

What are the 3 main uses of genetic screening

Answer 17

Identification of carriers-testing family history and can discover if a couple carriers a allele that can cause a disorder and can be used to make a informed decision on whether to have a child

Preimplantation genetic diagnosis-screening embryos before they are implanted in a woman which reduces chance of having a child with genetic disorders.avoids issue of abortion

Prenatal testing-screening unborn babies offered to women who have a history of genetic disorders

Question 18

What are some similarities and differences between amniocentesis and chorionic villus sampling

Answer 18

Amneocentesis
-carried out at 15-20 weeks pregnant
-1%chance of miscarriage
Sample obtained through amniotic fluid

CVS
-carried out at 11-14 weeks
1-2%of miscarriage
Obtained via the vagina

Question 19

What is genetic screening

Answer 19

Analysing DNA to see if it contains alleles for genetic disorders

Question 20

What is Epigenetics?

Answer 20

Genetic control by factors other than DNA sequence

Question 21

What chemical can silence a gene?

Answer 21

DNA methylation