Genetics

Question 1

What is a DNA double helix

Answer 1

Deoxyribose ( sugar )
Nucleic ( nucleotides )
Acid ( phosphate)

Question 2

What is the location and function of DNA

Answer 2

Found in nucleus
Carries all of our genetic material

Question 3

Describe the idea of nucleotides

Answer 3

Made up of 4 bases - adenine & thymine or guanine & cytosine
Adenine always pairs with thymine
Guanine always pairs with cytosine

Question 4

Describe the backbone of DNA

Answer 4

Nucleotides are linked together via the phosphate to form the back bone

Question 5

Describe the pattern of pairings with bonds

Answer 5

A-T are bonded using 2 hydrogen bonds
C-G have 3 hydrogen bonds between them

Question 6

Describe the replication process

Answer 6

DNA strand is unzipped by helicase which breaks the hydrogen bonds between the base pairs
The enzyme primase starts the process of rebuilding the separated strands
Primase makes a small piece of RNA which is a primer
DNA polymerase binds to primer to make new strands

Question 7

What is RNA

Answer 7

Has a backbone made with alternating phosphate groups and ribose which is different to DNA
Attached to each sugar in one of four bases - adenine, uracil, cytosine or guanine
Found in cells nucleus, cytoplasm and organelles

Question 8

What are chromosomes

Answer 8

Bundles of DNA
Tightly coiled strand of DNA around a histone
Histones are proteins which give structure to the long strand of DNA

Question 9

How many chromosomes are there

Answer 9

Most cells in the body contain 46 chromosomes and are in 23 homologous pairs
22 pairs are autosomal and the 23rd pair is sex determing

Question 10

What are diploid cells

Answer 10

All cells in the human body are diploid minus sperm and egg cells
Contain all of the genetic material
Contain the normal amount of pairs of chromosomes
Produced from identical versions of themselves
Reproduce identical versions of themselves

Question 11

What are haploid cells

Answer 11

Sperm and egg cells
Contain half of genetic material
Contain 23 chromosomes not pairs
Made by diploid cells via meiosis- producing 4 non identical versions of the cell
Each cell has a different set of genetic material so they aren’t exact copies

Question 12

What is a gene

Answer 12

Section of DNA that codes for a particular protein

Question 13

Explain genes and codons

Answer 13

There are between 20,000 - 25,000 genes in the human genome
Genes are made up of a series of nucleotide bases in a chain, from a few hundred to 2 million per gene
Codons are much smaller units and are chains of three base groupings

Question 14

What are alleles

Answer 14

Different versions of the same gene
If two alleles are identical are called homozygous
If two alleles are different are called heterozygous

Question 15

What are mutations

Answer 15

Alteration of bases in the genetic code

Question 16

What are single gene disorders

Answer 16

Autosomal dominant
Autosomal recessive
Sex linked recessive
Sex linked dominant

Question 17

What does autosomal and sex linked mean

Answer 17

Autosomal refers to the 22 non sex chromosomes
Sex linked refers to the 1 set of XX or XY chromosomes

Question 18

Show how to see dominant and recessive

Answer 18

R is dominant
r is recessive

Question 19

What is a phenotype

Answer 19

Observable physical property of an organism

Question 20

What are examples of autosomal dominant disorders

Answer 20

Achondroplasia ( dwarfism )
Huntingdon’s disease
Neurofibromatosis
Osteogenesis imperfecta

Question 21

What are examples of autosomal recessive disorders

Answer 21

Sickle cell
Thalassemia
Cystic fibrosis
Phenylketonuria (PKU)
Medium chain acyl CoA dehydrogenase deficiency (MCADD)

Question 22

How can someone have an autosomal recessive disorder

Answer 22

If both parents are carriers or have the condition for it to be present

Question 23

What are examples of X linked recessive disorders

Answer 23

Haemophilia
Duchene muscular dystrophy
Colour blindness

Question 24

What are examples of X linked dominant disorders

Answer 24

Fragile X

Question 25

What are examples of Y linked disorders

Answer 25

Related to male infertility

Question 26

What is co- dominance inheritance

Answer 26

Some genes may not show complete dominance but rather share the effect between the two alleles e.g. sickle cell disease

Question 27

What is multiple allele inheritance

Answer 27

Some genes have more than two alternate forms e.g. ABO blood groups

Question 28

What is polygenic inheritance

Answer 28

Most often several genes are responsible for any given trait e.g. eye colour
Diseases such as heart disease

Question 29

What is multifactorial inheritance

Answer 29

Since they involve a complex interaction of the environment e.g. cigarette smoke