genetic information

Question 1

define the term exon

Answer 1

bae sequence coding for a polypeptide

Question 2

define non coding sequence and describe where the non coding multiple repeats are positioned in the genome

Answer 2

1. DNA that does not code for amino acids
2. positioned between genes

Question 3

compare and contrast DNA in eukaryotic cells with the DNA in prokaryotic cells

Answer 3

1. (contrast)
   a. linear compared to circular
   b. associated with histones vs not
   c. no plasmids vs plasmids
2. (compare)
   a. both consists of nucleotides joined by phosphodiester bonds
   b. DNA in mitochondria and chlorplasts is similar to prokaryotes

Question 4

describe how a polypeptide is formed by translation of mRNA

Answer 4

1. Anticodon binds to complementary codon
2. tRNA binds to specific amino acid
3. amino acids join by peptide bonds
4. with the use of ATP
5. tRNA Is released
6. ribosome moves along mRNA

Question 5

describe the role of a ribosome in the production of a polypeptide (translation)

Answer 5

1. mRNA binds to ribosome
2. covers first two codons
3. allows tRNA anticodons to bind
4. moves along mRNA to next codon

Question 6

Explain a way other that crossing over and independent segregation that genetic variation in a species is increased

Answer 6

random fusion of gametes - produces new allele combinations

Question 7

Explain how chromosome number is halved during meiosis

Answer 7

homologous chromosomes
2. One of each homologous pair goes to each daughter cell

Question 8

Explain why all cells share a mutation

Answer 8

1. Mutation occurs in gamete which forms the zygote
2. All cells derived from zygote by mitosis
3. Mitosis produces genetically identical cells

Question 9

What is a codon

Answer 9

1. 3 bases of an mRNA
2. Code for an amino acid

Question 10

Explain why percentages of bases are different at middle of chromosome and end of chromosome

Answer 10

1. Have different base sequences
2. Transcribed from different DNA

Question 11

How can a mutation in a tumour suppressor result in formation of tumour

Answer 11

1. Gene cannot control cell division
2. Rate of cell division to fast

Question 12

How can a mutation lead to the production that has one amino acid missing

Answer 12

loss of a triplet

Question 13

How can a mutation lead to a nonfunctional enzyme

Answer 13

1. Change in base sequence of amino acids
2. Change in hydrogen/ionic bonds that hold up tertiary stricture
3. substrate cannot bind

Question 14

Describe what happens during division 1 in meiosis

Answer 14

1. Chromosomes in homologous pairs
2. Separated – one of each into daughter cells

Question 15

Explain the appearance of a chromosome

Answer 15

1. 2 sister chromatids held together by centromere
2. Due to DNA replication

Question 16

Describe what happens to chromosomes in meiosis

Answer 16

1. Formation of bivalents
2. Crossing over
3. Join to spindle at equator of cell via centromere
4. Move to opposite poles of cell
5. Chromatids separated in meiotic division II

Question 17

Why is it important that one chromosome from each homologous pair goes to each of the cells produced

Answer 17

1. To half the number of chromosomes
2. So that diploid number can be restored at fertilisation

Question 18

Explain the importance of meiosis in the life cycle of organisms which reproduce sexually

Answer 18

1. Half the number of chromosomes
2. So diploid number can be restored at fertilisation
3. Keep chromosome number constant from generation to generation

Question 19

State three comparisons of genetic diversity that the scientists used in order to generate classification Y

Answer 19

1. Base sequence of DNA
2. Base sequence of amino acids
3. Base sequence of mRNA

Question 20

There are many different species of field mouse in Europe. Using a phylogenetic classification, all of these species have names that start with apodemus. What information does this give about field mice?

Answer 20

1. All belong to the same genus
2. Share a common ancestor

Question 21

How can a sampling procedure be standardised when collecting flies

Answer 21

same size net

Question 22

When scientists collected bees what is one consideration, they had to take into account to ensure their method allowed them to identify the species they belonged to

Answer 22

must allow close examination

Question 23

Why would the index of diversity of insects be higher in a hedge rather then open field

Answer 23

1. More plant species
2. More food sources
3. More habitat/niches

Question 24

Scientists collected animals from soil samples from 40 minutes. Suggest how the scientists decided that 40 minutes was an appropriate time

Answer 24

1. Repeat soil sorting for different times and record number of species collected
2. Find optimum time which further sorting does not lead to increase in animal species found

Question 25

The genetic diversity of species is measured by comparing differences in the base sequence of DNA or differences in the base sequence of mRNA. Give 2 other ways in which genetic diversity between species is measured

Answer 25

1. Comparing amino acid sequence 2. Comparing observable characteristics

Question 26

If asked for the chnage in DNA for a mutation…

Answer 26

state what base has been substituted/deleted/added

Question 27

what can you conclude about the relationship between ambystoma tigrinum and ambystoma mexicanum and give a reason

Answer 27

1. they both belong to the same genus 2. because both names start with ambystoma 3. they share a common ancestor

Question 28

if shown a graph and asked what type of selection something is

Answer 28

(if stabilising selection) 1. mean size favoured 2. because graph is bell shaped