Genetic Information, Variation And Relationships Between Organisms

Question 1

What is a gene?

Answer 1

A section of DNA that contains coded information for making polypeptides and functional RNA.
It is located at the locus.

Question 2

What is the genetic code?

Answer 2

Degenerate code because the amino acids are coded for by more than one triplet code.
Some triplets are stop coded.
Code is nonoverlapping.
This code is universal.

Question 3

The structure of a chromosome.

Answer 3

Two threads each called chromatid joined at a centromere.

Question 4

What is a homologous chromosomes?

Answer 4

Sexually produced organisms have these because it’s a fusion of two different sets of chromosomes.
13 from each parent known as homologous pairs in diploid number.

Question 5

What is an allele?

Answer 5

One of an alternate forms of genes.
Each individual gets one allele from each parent.
Any changes in the base sequence produces a new allele of that gene due to mutation.

Question 6

What is a genome?

Answer 6

Complete set of genes in a cell including the mitochondria and chloroplasts.

Question 7

What is a proteome?

Answer 7

Full range of protein produced by the genome.

Question 8

What is RNA?

Answer 8

Polymer made up of repeating mononucleotide subunits.
Single strand.
It is made up of:
-pentose sugar ribose
-organic base (uracil replaces thymine)
-phosphate group.

Question 9

Types of RNA.

Answer 9

Messenger RNA.

Transfer RNA

Question 10

What is mRNA?

Answer 10

Long strand which is single helix.
Base sequence is determined by DNA by a process called transcription.
Once formed mRNA leaves the nucleus then it acts as a template for protein synthesis.

Question 11

What is tRNA?

Answer 11

Relatively small molecule made up of 80 nucleotides.

Single stranded chain folded into a clover leaf shape so amino acids can easily attach to the anticodon.

Question 12

Describe the process of transcription.

Answer 12

An enzyme acts on a specific region of the DNA causing the strands to separate and expose the nucleotide bases.
These bases are known as the template strand, and they pair with their complimentary bases from the pool in the nucleus.
These bases are joined by RNA polymerase forming pre-mRNA.
The DNA strand rejoins as this happens.
When RNA polymerase reaches a stop codon it detaches and pre-mRNA is complete.

Question 13

Describe the splicing of pre-mRNA.

Answer 13

This is when pre-mRNA becomes mRNA.
Introns are removed from exons.
Exons are joined together.
After this the mRNA leaves via nuclear pore.

Question 14

Describe the processes of translation.

Answer 14

A ribosome becomes attached to the starting codon at one end of the mRNA.
The tRNA molecule with complementary anticodon sequence moves to the ribosome and pairs up with the codon on the mRNA.
The ribosome moves along the mRNA joining two molecules of tRNA at any given time.
The tRNA is then joined by a peptide bond by an enzyme and ATP.
This goes on until the ribosome reaches a stop codon, mRNA and tRNA separate and polypeptide chain is complete.

Question 15

What is a mutation?

Answer 15

Any change to the quantity or base sequence of the DNA of an organism.
They occur constantly and usually result in no physical change.

Question 16

Types of mutation in genetic code.

Answer 16

Substitution
Deletion
Addition

Question 17

Describe the importance of meiosis and sexual reproduction.

Answer 17

Two gametes fuse together to give new offspring.
Each has a haploid number of chromosomes which becomes diploid.
This gives genetic variation due to crossing over.

Question 18

Describe the process of meiosis.

Answer 18

In the first division (meiosis 1) homologous chromosomes pair up and their chromatids wrap around eachother this is called crossing over, these pairs then separate.
Second meiosis dividion the chromatids move apart so that 4 cells have been formed with 23 chromosomes, these are non identical.

Question 19

What is genetic diversity?

Answer 19

The total number of different allele in a population.

Question 20

Describe the process of natural selection.

Answer 20

In any population there is a gene pool.
Random mutation will result in a new allele.
These individuals may become better adapted and survive to breeding age to pass on allele.
Therefore the next generation is better adapted too.
This goes on till all worse adapted species die.

Question 21

Types of selection.

Answer 21

Directional selection

Stabilising selection

Question 22

What is directional selection?

Answer 22

A spontaneous mutation causes the species to be better adapted to a change in environment.
Moving the majority of individuals towards this allele.

Question 23

What is stabilising selection?

Answer 23

This is when an advantageous allele becomes even more advantageous due to a harsher environment.

Question 24

What is a species?

Answer 24

Capable of breeding to produce loving fertile species.

Question 25

How to name species?

Answer 25

By the binomial system.
First name is the generic name and denotes the genus, this is always written with a capital.
The second name is the specific name and denotes the species, this is written with a lower case.

Question 26

What is courtship behaviour?

Answer 26

A courtship display is a set of display behaviors in which an animal attempts to attract a mate and exhibit their desire to copulate

Question 27

Why is courtship behaviour important?

Answer 27

Recognise members of their own species.
Identify a mate that is capable of breeding.
Form a pair bond.
Synchronise mating.
Becoming able to breed.

Question 28

What is artificial classification?

Answer 28

Dividing organisms according to differences that are useful at the time.
Analogous characteristics which have the same function but different evolutionary origins.

Question 29

What is phylogenetic classification?

Answer 29

Based on evolutionary relationships.
Classification of species using shared feature derived from ancestors.
Arranged groups into a hierarchy.

Question 30

What is a hierarchy?

Answer 30

Groups within other group with no overlaps.

Question 31

Name the order of taxonomy.

Answer 31

Domain
Kingdom
Phylum 
Class 
Order
Family
Genus
Species
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Question 32

The three main domains.

Answer 32

Bacteria, single prokaryotes
Archaea, group of prokaryotes
Eukarya, eukaryotes

Question 33

Ways of investigating diversity.

Answer 33

Comparison of observable characteristics.
Comparison of DNA bases.
Comparison of base sequence of mRNA.
Comparison of amino acids sequences in proteins.

Question 34

Quantitative investigation of variation.

Answer 34

Random sampling