Genetics LO

Question 1

Describe the structure and function of DNA

Answer 1

• Long molecules
• Double stranded made of two chains of nucleotides
• nucleotide consists of three subunits: sugar, phosphate, base
• contains genetic material

Question 2

Describe the structure and function of RNA

Answer 2

• made of ribose sugar, phosphate, base
• A, U, G, C
• present in all living cells
• structurally similar to DNA but is single stranded
• involved in regulating gene expression

Question 3

Describe the structure and function of genes

Answer 3

• made of bases known as codons
• each codon has a protein
• full set of genes = genome
• decoded by transcription and translation
• code for organisms individual characteristics

Question 4

Describe the structure and function of chromosome

Answer 4

• tightly coiled strand of DNA around a histone
• most cells contain 46 chromosomes, 23 pairs
• paired copies of genes = homologous chromosomes
• sex cells = haploid

Question 5

Define the term allele

Answer 5

Multiple versions of the same chromosome

Question 6

Define the term locus

Answer 6

The place on the chromosome when the gene is located

Question 7

Define the term genotype

Answer 7

The genetic constitution of an organism

Question 8

Define the term phenotype

Answer 8

The observed characteristic coded for by the genotype

Question 9

Define the term homozygous

Answer 9

When two chromosomes are the same

Question 10

Define the term heterozygous

Answer 10

When the two chromosomes are different

Question 11

Define the term dominance

Answer 11

Only one allele is required for the characteristic to be expressed in the phenotype

Question 12

Define the term recessive

Answer 12

Both alleles are are required for the characteristic to be expressed in the phenotype

Question 13

Define the term co-dominance

Answer 13

Both alleles are dominant to a degree and are both expressed in the phenotype

Question 14

Define the term homologous chromosomes

Answer 14

Paired copies of the same chromosome

Question 15

Define the term mutation

Answer 15

An alteration of bases in the genetic code

Question 16

Define the term autosomal

Answer 16

Chromosomes which aren’t sex chromosomes

Question 17

Define the term sex chromosomes

Answer 17

Chromosomes that determine your sex, can carry other sex linked characteristics

Question 18

Rules for a Punnett square

Answer 18

1) write (diploid) genotype of adult of box (usually female on top)
2) write possible genotype
3) write combination in each box to represent

Question 19

Define the term polygenic

Answer 19

Most often several genes are responsible for any given trait

Question 20

Define the term multifactorial

Answer 20

When a number of genetic and environmental factors affect the characteristic expressed by the gene

Question 21

Differentiate between mitosis and meiosis

Answer 21

Mitosis - occurs in all organisms, creates body cells, one cell division, no recombination or crossing over, produces 2 diploid identical daughter cells
Meiosis - occurs in animals, plants + fungi, creates sex cells, two cell divisions, recombination/crossing over in prophase, produces 4 haploid cells, genetically different
Both - creates new cells, follow same steps, begin with one parent cell

Question 22

Describe antenatal screening tests and their relevance to genetics: sickle cell trait, thalassaemia, Down syndrome, neural tube defects

Answer 22

• Antenatal screening tests find out if your baby has a higher chance of having a genetic condition
• Can be a range of tests including: blood tests and ultrasounds

Question 23

Describe the role of the genetic counsellor and the specialist service

Answer 23

A genetic counsellor gives you information about how genetic conditions might affect you or your family