GENETICS 1

Question 1

what is a phenotype

Answer 1

this is the outward and physical manifestation of an organism

Question 2

what is a genotype

Answer 2

this is the full hereditary information of an organism even if not expressed .

Question 3

what is the relationship between DNA structure an d function

Answer 3

DNA is transcribed into mRNA and then translated into proteins in the ribosome .

Question 4

what is the structure of a DNA

Answer 4

made up of a pentose sugar , phosphate group and a nitrogenous base .

Question 5

what is a nucleoside

Answer 5

a base and a pentose sugar

Question 6

bonds involved in a DNA molecule

Answer 6

there is hydrogen bonds that are formed between the nitrogenous bases.

Question 7

what are purines

Answer 7

they are adenine and guanine

Question 8

what are pyrimidines

Answer 8

they are thymine , cytosine and uracil in the RNA .

Question 9

complementary base pairing the number of bonds that are formed

Answer 9

3 bonds for cytosine and guanine
2 bonds for adenine and thymine

Question 10

the largest organelle in animals

Answer 10

the nucleus which contains the DNA

Question 11

site for DNA replication

Answer 11

nucleus

Question 12

site for DNA transcription

Answer 12

nucleolus

Question 13

what are chromosomes

Answer 13

they are wound DNA that are packed together into a thread like structure.

Question 14

length of the DNA

Answer 14

2m

Question 15

what are the parts of a chromosome

Answer 15

the two sister chromatids that are joined together by the centromere.

Question 16

how many chromosomes are present in a human cell

Answer 16

humans have 23 pairs of chromosomes with 22 pairs being autosomal while 1 pair the 23rd being sex chromosome

Question 17

how does the DNA achieve the structure to be able to be packaged into a chromosome.?

Answer 17

they are tightly wound on histone proteins to form a nucleosome

Question 18

what is a nucleosome

Answer 18

DNA that is wound around a histone protein.

Question 19

what does a nucleosome comprise of

Answer 19

comprises of eight histone proteins around which the DNA wraps 1.65 times

Question 20

chromatin

Answer 20

mixture of DNA ,(histone) proteins and RNA which package within the nucleus.

Question 21

heterochromatin

Answer 21

the condensed regions of the chromatin

Question 22

euchromatin

Answer 22

the extended form of the chromatin

Question 23

process of DNA transcription and replication

Answer 23

1.both require the unzipping and closure of the DNA helix structure this is done by the enzyme ligase and the enzyme helicase.
2. the histone wrapping at the nucleosome has to be altered to expose more genes for the processes.
3. this is done by the addition of other molecules.
4.this is a reversible process .

Question 24

modifications of the histone

Answer 24

addition of a methyl group
addition of an