Genetics

Question 1

What is DNA?

Answer 1

the molecule that contains the genetic information used in the development and functioning of all living organisms

Question 2

What are chromosomes?

Answer 2

dense structures of tightly coiled DNA that become visible during division

Question 3

What is a gene?

Answer 3

-a sequence of DNA that functions as unit of genetic information
-this section is located between a start codon and stop codon

Question 4

What is a genotype?

Answer 4

the genetic total extent of the genetic information we carry

Question 5

What is a phenotype?

Answer 5

this is what genetic information is actually expressed in our physical appearance or outward characteristics

Question 6

What does each chromosome form?

Answer 6

chromosome pairs, therefore we have a pair of genes of each characteristic

Question 7

What are alleles?

Answer 7

alternative versions of the same gene

Question 8

What does homozygous and heterozygous mean?

Answer 8

-homozygous= person carries the same allele on each homologous chromosome

-heterozygous= person carries different alleles on each homologous chromosome

Question 9

Explain the process of protein synthesis

Answer 9

1. information contained in a specific region of DNA is copied (transcribed) to produce a specific molecule of RNA
2. RNA attaches to a ribosome where the information in the RNA is translated into specific amino acids to form a new protein molecule

Question 10

What is a triplet codon?

Answer 10

three bases which carry the genetic code of instructions which codes for a single amino acid

Question 11

What are the 3 types of RNA made from DNA?

Answer 11

-Messenger RNA (mRNA)
-Ribosomal RNA (rRNA)
-Transfer RNA (tRNA)

Question 12

What is inheritance?

Answer 12

the passage of hereditary traits from one generation to the next

Question 13

How many pairs of chromosomes does the nuclei of all human cells contain?

Answer 13

23 pairs (the diploid number) , one chromosome in each pair came from the mother and one from the father

Question 14

What are the 4 nucleotide bases in DNA?

Answer 14

Adenine
Guanine
Cytosine
Thymine

Question 15

What is a complementary strand of DNA?

Answer 15

-the nucleotides bind in pairs: A binds with T, and C binds with G
-therefore the coding strand and complementary strand are made up of these complementary matches

Question 16

What does the process of mitosis produce?

Answer 16

two genetically identical daughter cells that have the same number of chromosomes as the original cells

Question 17

What does the process of meiosis produce?

Answer 17

four daughter cells that have half the number of chromosomes as the original cell, all genetically different

Question 18

What is the difference between dominant and recessive alleles and how are these expressed in a punnet square?

Answer 18

-where 2 different alleles may be present in the genotype, usually one is dominant and becomes expressed in the phenotype, and one is recessive and remains dormant within the genotype

-dominant alleles are abbreviated with a capital letter e.g T and recessive alleles are abbreviated with a lowercase letter t

-you have to have 2 recessive alleles for the recessive genotype to be expressed

Question 19

What is phenylketonuria (PKU) and what type of condition is this?

Answer 19

-condition where unable to produce enzyme phenylalanine hydroxylase (PAH) due to non functional allele for this enzyme causing problems with metabolism and neuronal developement

-its an autosomal recessive, therefore there’s a 25% chance in developing the condition (aa)

Question 20

What is Huntingdon’s disease and what type of condition is this?

Answer 20

-a genetically inherited disease of the brain that damages nerve cells causing a gradual deterioration in cognitive function

-its a autosomal dominant condition

-50% will develop the condition and 50% will be unaffected

Question 21

what is a sex linked condition giving an example

Answer 21

-these conditions are found on the sex chromosomes, XX = girl, XY= boy

-red green colour blindness are unable to distinguish shades of red and green

-as this condition expresses its allele on the X chromosome, males only need one defective allele for the condition to develop

Question 22

What is co-dominance?

Answer 22

some genes may not show complete dominance but rather share the phenotype between two alleles e.g AB blood group

Question 23

What is genetic imprinting?

Answer 23

involves a sex-specific process of chemical modification to the gene so that the alleles are unequally expressed depending on the sex of the parent carrying the modified gene

Question 24

What does polygenic mean?

Answer 24

most often several genes are responsible for any given trait e.g skin colour

Question 25

what does multifactorial mean?

Answer 25

they involve a complex interaction of the genes with the environment

Question 26

What is epigenetics?

Answer 26

-the study of changes in organisms caused by modification of gene expression rather than alteration of the genetic code itself

Question 27

What modifications can be made to gene expression?

Answer 27

adding molecules e.g methyl groups to DNA, changing the structure of DNA but not the sequence, altering how the gene interacts during transcription

Question 28

What is genetic counselling?

Answer 28

a service that provides support, information and advice about genetic conditions

Question 29

Give examples of what genetic counselling includes

Answer 29

-providing information on the genetic condition that affect the family

-calculating risk of passing inherited condition to their children

-discussing risks, benefits and limitations of genetic testing