Unit 4 Genetic Diversity and Adaptation

Question 1

What is the definition of a mutation?

Answer 1

A change to the quantity or the base sequence of the DNA of an organism

Question 2

What is a gene mutation?

Answer 2

A change to a sequence of nucleotides or bases within DNA

Question 3

Two methods of a gene mutation?

Answer 3

Substitution or deletion

Question 4

What is the general effects of substitution gene mutation? General Effects

Answer 4

A replacement of a nucleotide in the base / nucleotide sequence - change the whole sequence - the triplets are affected - the polypeptide the codes - Different amino acid - function of the protein is not met.

Question 5

Give an example of how a substitution gene mutation could really affect a protein in the human body?

Answer 5

A replacemet of a nucleotide in the nucleotide sequence - whole sequence is changed - the polypeptide is changed - the protein forms an enzyme- the tertiary structure of this enzyme changed- the active site of the enzyme - can’t fit the substrate.

No ES Complexes can be formed

Question 6

Explain gene mutation deletion in general terms?

Answer 6

The loss of a nucleotide - hcanges the whole nucleotide sequence - polypeptide is different - cannot function correctly

Question 7

What are chromosome mutations?

Answer 7

Changes in the structure or the number of whole chromosomes.

Question 8

What is polyploidy and where does it usually occur?

(Changes in the whole sets of chromosomes)

Answer 8

When organisms have 3 or more sets of chromosomes than the usual 2 chromosomes

Usually occurs in plants

Question 9

What can changes in the individual chromosomes lead to?

Answer 9

Thus individual pairs of chromsomes fail to separate during meiosis - leads to non-disjunction

Question 10

Non-disjunction means?

Answer 10

Non-disjunction means that an organism has a gamete containing one fewer or more of a chromosome.

This means during fertilisation the fusion of a normal gamete and that gamete - resultant offspring have more of fewer number of chromosomes in their body cells

Question 11

What is an example of non-disjunction in the human body?

Answer 11

Down’s Syndrome which means that the human body has an additional chromsome

Question 12

What is mitosis?

Answer 12

Production fo 2 identical daughter cells which contain the sam enumber of chromosmes as the parent cell

Question 13

What is meiosis?

Answer 13

Cell Division that leads to the production of 4 non-identical haploid cells which have different number of chromosmes than the parent cell.

Question 14

Why is meiosis important?

Answer 14

Meiosis means that there is production of gametes which then fuse together during fertilisation.

Question 15

What is different about the mitosis and meiosis cycles within a fern plant?

Answer 15

Mitosis produces the gametes and meiosis produces the spores

Question 16

Describe the properties of the diploid cell of an organism?

Answer 16

Diploid cell contains the 2 complete sets of chromosomes - 2 individual sets are provided by the parents

Question 17

Describe what happens to the diploid cell during the meiosis cycle?

Answer 17

The homologous pairs start to separate so that only one chromosome from each pair enters the daughter cell.

Question 18

What restores the haploid number back to the diploid number

Answer 18

When the process of fertilization occurs the haploid cells from either gametes of the parents fuse so that it forms the diplolid cells.

Question 19

What is the human body number for the haploid number?

Answer 19

23

Question 20

What are the 2 general steps within the process of meiosis?

Answer 20

1) The first divison in which the homologous chromosomes pair up and then are separated astheir chromatids cross over which leads to a process called crossing over.

2) The second division in which the chromatids are separated which produces 4 non-identical daughter cells

Question 21

What is the importance of crossing over in any organism?

Answer 21

Crossing over allows th random genetic variation within an organism to be established.

Question 22

What are the 2 ways in which genetic variation within an organism can be achieved?

Answer 22

1) Independent segregation of homologous chromosomes

2) New combinations of maternal and paternal alleles via crossing over

Question 23

What is a gene?

Answer 23

A length of DNA that carries the code to make a polypeptide and therefore a protein

Question 24

What is a locus?

Answer 24

The position of a gene on a chromosome or strand of DNA

Question 25

What is an allele ?

Answer 25

One or more different variations of a gene

Question 26

What is a homologous chromosome?

Answer 26

A pair of chromosomes that comes from the maternal and paternal parents which have the same gene loci point

Question 27

Describe in greater detail the gentic recombination of the genes crossing over?

Answer 27

1) The chromatids of each pair become twisted around each other

2) Whilst twisting - tensions are created and portions of the chromatids break off

3) these broken pieces of the chromatids rejoin with the homologous chromosome pairs

4) Usually there are equivalent portions of the chromosomes that are exchanged between the homologous chromosome

5) So there are new genetic combinations are formed from the maternal and paternal parents which leads to an increase in the number of alleles

Question 28

What does an increase in the numbe rof alleles within a population lead to?

Answer 28

An increase number of alleles increases the genetic variation within the gene pool - more easuily able to adapt to the change in environment so survival and reproductive adavantage