unit 2 AOS 1

Question 1

gene?

Answer 1

A gene is a length of DNA that contains the code instructions for building a gene product (usually a polypeptide)

segments of DNA

A section of DNA that has a functional purpose, such as coding for a protein that determines a trait.

Question 2

chromosomes

Answer 2

A thread-like structure composed of DNA and protein

Question 3

DNA

Answer 3

allows a great deal of genetic information to be stored in a cell.

Question 3

histone

Answer 3

a protein found in eukaryotic chromosomes that assist in packaging the DNA

Question 4

nucleosome

Answer 4

a section of supercoiled DNA around histones

Question 5

chromatin

Answer 5

a mass of genetic material composed of DNA and proteins that condense to form chromosomes during eukaryotic cell division

- The coiling of DNA round histones to form nucleosomes enables the huge quantity of DNA condense. This condensed DNA is now known as chromatin

Question 6

Eukaryotic chromosome structure

Answer 6

• Eukaryotic chromosome are composed of two main ingredients - DNA and proteins, called histones

During mitosis and meiosis, the chromosomes are remodelled into highly condensed (compact) chromosomes

Question 6

Prokaryotic chromosome structure

Answer 6

Prokaryotic cells also have DNA packaged into chromosomes. However their DNA is usually in the form of a singular chromosome

- The single chromosome is less condensed compared to DNA  in eukaryotic Histones are not used in the supercoiling process 

- DNA in prokaryote's are still coiled tightly, forming the distinctive loops and twists

Question 7

Allele

Answer 7

The different forms of a particular gene

- The gene with a different sequence of nucleotides is called an allele of that gene 

- E.g. hair colour - everyone has a hair colour, but people have different alleles of that gene (someone may have red hair, other may have black, different alleles)

- Everyone has two alleles of every gene. The allele from the mum is called the maternal allele. The allele from the dad is called the paternal allele

Question 7

Genome

Answer 7

The complete set of genetic material in a cell of an organism

- The full set of genetic information in whatever is being discussed. For example if talking about the genome of a person, then its all the genetic information contained within the cells of that person

Question 8

genotype

Answer 8

the set of alleles that an individual has

Question 9

Phenotype

Answer 9

the physical appearance of a trait; determined by which alleles are present

• A combination of the genotype and environmental factors

Question 10

karyotypes

Answer 10

A karyotype is a photograph of a persons chromosomes

- Karyotypes can be used to determine a number of things about an individual, including:
· Sex - x and y chromosomes
· Species 
· Some genetic abnormalities

Question 11

centromere

Answer 11

the position where the chromatids are held together in a chromosome.

Question 11

autosome

Answer 11

any one of a pair of homologous chromosomes that are identical in appearance in both males and female.

- Non sex chromosomes

Question 12

Homologous

Answer 12

matching pairs of chromosomes that have the same genes at the same positions.

Humans have 23 pairs of homologous chromosomes

Question 13

Environmental sex determination (ESD)

Answer 13

the sex of the offspring is established by environmental conditions rather than genetic factors.

Question 14

Locus

Answer 14

the position of a gene on a chromosome; plural = loci.

Question 15

Non-homologous

Answer 15

non-matching chromosomes.

Question 16

Sex chromosomes

Answer 16

a pair of chromosomes that differ in males and females of a species; allosomes.

last pair of chromosomes that determine the gender