Genetic information, variation and relationships between organisms

Question 1

What are chromosome mutations?

Answer 1

Changes in structure or number of whole chromosomes:

• arise spontaneously
• Change in whole sets of chromosomes
• when organisms have 3 or more sets of chromosomes rather than the usual 2 (Called polyploidy - occurs mostly in plants)

Changes in number of individual chromosomes:
-Homologous pairs of chromosomes fail to separate in meiosis (non-disjunction)
result- Gamete will often have 1 more or 1 less chromosome(s)
-After fertilisation offspring will have fear/more chromosomes

Question 2

What is splicing?

Answer 2

Pre-mRNA is made from introns and exons (In eukaryotic cells)
Introns do not code for proteins and must be removed by splicing
splicing removes introns and joins exons together to create mRNA

Question 3

What is gene mutation?

Answer 3

Any change to 1 or more nucleotide bases or any rearrangement of bases
gene mutations arise spontaneously during DNA replication(base deletion/substitution)

Degenerate nature of genetic code means not all bas substitution causes a change in sequence of amino acids

Question 4

What is comparison of observable characteristics?

Answer 4

Traditional - based of the fact that each observable characteristic is determined by genes
The variety within a characteristic depends on the number and variety of alleles of that gene (plus environmental influences)

Limited because large amount of observable characteristics are coded for by more than one gene (Polygenic)
Also because environment can have an impact on these characteristics)

Question 5

Examples of Conservation techniques?

Answer 5

• Maintain existing hedgerows at most beneficial height/shape
• Plant hedges as field boundaries rather than fences
• Reduce use of pesticides
• Use organic rather than inorganic fertilisers
• Maintain existing ponds and create new ones

Question 6

What are ways of comparing genetic diversity?

Answer 6

• Comparison of observable characteristics
• Comparison of DNA base sequence
• Comparison of mRNA base sequence
• Comparison of amino acid sequence of a protein

Question 7

What practices reduce species diversity?

Answer 7

Directly:
-Remove hedgerows and grubbing out woodland
-Creating monocultures e.g replacing natural meadows
with cereal crops
-Filling in ponds and draining marsh
-Over-grazing of land

Indirect:

• Use of pesticides and inorganic fertilisers
• Escape of effluent into eater courses
• Absence of crop rotation

Question 8

What is substitution of bases?

Answer 8

The type of gene mutation in which a nucleotide is replaced by another nucleotide with a different base - doesn’t always have an effect on amino acid (degenerate/could be an intron)

Question 9

What is deletion of bases?

Answer 9

Arises when a nucleotide is lost from a base sequence
Whole base sequence following deleted base moves back one place (Frame shift) which changes most of the triplets

will n lead to different sequence of amino acids so normally = non-functional polypeptide

Question 10

What is the genetic code?

Answer 10

Genetic code of an organism is the sequence of bases a long it’s DNA
Contains thousands of genes -each gene codes for a specific protein
The sequence is read in groups of 3 bases (triplets), each triplet codes for a specific amino acid

Question 11

How is prokaryotic DNA different to eukaryotic?

Answer 11

Prokaryotic:

• DNA is shorter
• Circular
• Not associated with proteins
• Don’t contain introns

Eukaryotic

• Longer DNA
• Linear
• Occur in association with histones(proteins) to form chromosomes
• Contain introns

Question 12

What is comparison of DNA base sequence?

Answer 12

Can now read sequence of DNA to measure genetic diversity of determine evolutionary relationships by looking at how similar or different genes are

Question 13

What is comparison of mRNA base sequence?

Answer 13

mRNA is coded for by DNA so sequencing it can give base sequence of DNA
Can also be easier to isolate from the cell

Question 14

What is comparison of amino acid sequence of a protein?

Answer 14

Amino acids are determined by mRNA which is determined by DNA
Therefore genetic diversity can be measured by comparing amino acid sequence

Question 15

What is a species?

Answer 15

Organisms that are able to breed and produce fertile offspring
Basic unit of classification

Question 16

What is a population?

Answer 16

A group of species in a certain area

Question 17

What is transcription?

Answer 17

1. DNA helices breaks hydrogen bonds between bases, causing double helix to separate
2. The exposed bases form template strand to RNA
3. Complimentary RNA bases are paired up (Instead of T adenine pairs with Uracil)
4. RNA bases are joined by RNA polymerase
5. when RNA polymerase reaches stop code it detaches. - this molecule is pre-mRNA
6. Splicing

Question 18

What is translation?

Answer 18

1. Once splicing is completed mRNA passes through nuclear pores and attaches to ribosome
2. tRNA molecule with complimentary anticodon moves to ribosome and pairs up with complimentary codon on mRNA
3. Ribosome reads next codon and this is repeated
4. Amino acids on tRNA are joined together by ribosome and peptide bonds are formed using an enzyme and ATP
5. Ribosome moves along mRNA and this is continued until top codon is reached and polypeptide is finished.