GEN1 - Key Terms and Concepts in Genetics and Genomics

Question 1

Define genetics.

Answer 1

Study of single or multiple genes and how they affect characteristics (e.g. phenotype).

Question 2

Define genomics.

Answer 2

Studying of all genetic information, not solely the genes. Includes non coding regions, regulatory regions, repetitive repeats etc.

Question 3

What are genes?

Answer 3

Considered the units of hereditary. Sections of DNA coding for proteins or functional RNA molecules.

Question 4

What chromosomes are found in a human cell?

Answer 4

Nuclear chromosome - main genome consisting of 23 pairs.

Mitochondrial chromosome - additional smaller circular chromosome.

Question 5

What word describes a location on a chromosome?

Answer 5

Loci.

Question 6

Discuss process occurring from genes to proteins.

Answer 6

Genes undergo transcription to form mRNA. This is dependent on promoter regions, transcription factors and gene accessibility. Mature mRNA undergoes splicing and processing. The mature mRNA is then translated into protein by membrane bound or free ribosomes.

Question 7

Give five types of functional RNA.

Answer 7

rRNA
tRNA
miRNA
ncRNA
siRNA

Question 8

Define haploid and diploid with examples.

Answer 8

Haploid - cells with half the genetic information - gametes.

Diploid - cells with full genetic information - somatic cells.

Question 9

Why are gametes haploid?

Answer 9

Ensures that genetic information within somatic cells remains at a constant level.

Question 10

How much of the entire genome codes for genes/proteins?

Answer 10

20,000 genes present within the genome. Approx 25% of whole genome is for genes.

However, only 2% of the whole genome is for proteins/RNA - these are the exons.

Question 11

Define the transcriptome and if it varies between cells.

Answer 11

Refers to RNA within cells - some definitions include both protein and non protein coding RNA.

Varies between cells as differing levels of gene expression are apparent.

Question 12

Define the exome and if it varies between cells.

Answer 12

Includes all exons within the genome. Does not vary between cells.

Question 13

Define the proteome and if it varies between cells.

Answer 13

Refers to all the proteins expressed within a cel. Varies between cells.

Question 14

What was Mendels key discovery?

Answer 14

Genes as the units of hereditary.

Question 15

What was discovered as a result of Mendels discovery?

Answer 15

DNA, genome, link to diseases/traits.

Question 16

Define genotype and phenotype.

Answer 16

Genotype - genetic makeup.

Phenotype - observable feature.

Question 17

Define heterozygous and homozygous.

Answer 17

Heterozygous - contains two different versions of a gene.

Homozygous - contains two same versions of a gene.

Question 18

Define recessive and dominant.

Answer 18

Recessive - two copies required for phenotype observation.

Dominant - one copy required for phenotype observation ONLY.

Question 19

Give two types of homozygosity.

Answer 19

Recessive or dominant. E.g. aa or AA.

Question 20

What is needed to observe Mendelian ratios in an experiment?

Answer 20

Large sample size - ratios can only be observed with enough offspring.

Question 21

What is sickle cell disease?

Answer 21

Autosomal recessive condition causing sickling of haemoglobin. Reduces oxygen delivery. Associated with anaemia. Can block blood vessels.

Question 22

Define and differentiate forward and reverse genetics.

Answer 22

Forward genetics - observing phenotypes to deduce the underlying genotype.

Reverse genetics - altering genotype (expression of gene or genetic modification) and observing the phenotype.

Question 23

Give differences between normal and sick cell patients at clinical, cellular and molecular level.

Answer 23

Clinical - normal have no symptoms vs affected susceptible to infections/anaemia.
Cellular - normal have disc shaped RBC vs affected have sickle shaped RBC.
Molecular - normal have normal Hb vs affected have aggregated Hb.

Question 24

What protein chains are within Hb?

Answer 24

Two alpha protein chains.

Two beta protein chains.

Question 25

What is observed during electrophoresis of normal vs sickle Hb and why?

Answer 25

Differing migration speeds through gel. Hb-S is more positive therefore migrates faster towards the anode. Hb-A is more negative so migrates slower towards the anode.

Question 26

What type of haemoglobin is found in sickle cell trait individuals?

Answer 26

Both normal and sickle haemoglobin found in patients with sickle cell trait.

Question 27

What changes are present within sickle haemoglobin and how were they discovered?

Answer 27

Peptide sequencing revealed change from glutamine to valine at 6th amino acid position in beta globin protein chain. Nucleotide sequencing revealed change from GAG to GTG causing the amino acid change.

Question 28

Are sickle cell trait individuals (a)symptomatic? Does this change?

Answer 28

Generally asymptomatic. Hypoxic conditions can cause aggregation of Hb-S present which cannot be overcome by HbA.

Question 29

Discuss link between sickle cell disease and malaria.

Answer 29

Sickle cell disease has high incidence in malaria prone regions - SCD provides increased resistance to malaria.

Question 30

What are the three classifications of genetic diseases? Describe each.

Answer 30

Monogenic - genetic conditions caused by single gene mutations and show Mendelian inheritance. Polygenic - genetic conditions caused by multiple gene mutations so do not show Mendelian inheritance. Acquired - mutations arise that are not present in parents, causing genetic disease.

Question 31

What are the five classes of monogenic diseases? Describe each.

Answer 31

Autosomal recessive - two copies needed on either autosome pair. Autosomal dominant - one copy needed on either autosome pair. X-linked recessive - two allele needed in females but only one in males (affects males more). X-linked dominant - one allele needed. Mitochondrial - passed by mother but can affect both genders.

Question 32

How can polygenic diseases be studied?

Answer 32

Use of genome wide association studies.

Question 33

Give examples of polygenic diseases.

Answer 33

Heart disease. Diabetes. Obesity.

Question 34

What factors increased chance of acquired genetic diseases?

Answer 34

Exposure to mutagens. Viral infections.

Question 35

What is the effect of mutations arising in somatic cells and germ cells, on acquired genetic diseases?

Answer 35

Mutation in somatic cell - common cause of cancer - not passed onto offspring. Mutation in germ cell - can be passed onto offspring - can result in de novo mutations.

Question 36

Aside from genotype, what two factors largely affect phenotype?

Answer 36

Environmental influences. | Epigenetic changes.

Question 37

Give three classes of agents that can cause environmental influences on the phenotype. Give example for each.

Answer 37

Chemical agent - pollutants. Physical agents - UV light. Biological agent - viral infections.

Question 38

What is the difference between minor and major phenotypic changes?

Answer 38

Minor phenotypic change - benign mole formation. | Major phenotypic change - cancerous tumour formation.

Question 39

Give examples of environmental influences that directly alter gene expression.

Answer 39

``` Temperature Pressure Irradiation Oxygen levels Diet Toxins ```

Question 40

When is a disease described as multi factorial?

Answer 40

Various genes and environmental influences affect the disease onset, severity, risk etc.

Question 41

Define the epigenome.

Answer 41

Complete set of epigenomic tags on the genome,

Question 42

Does the epigenome alter any of the following: transcriptome, genome, phenotype, exome, proteome.

Answer 42

Transcriptome - yes as genes undergoing transcription are changed. Proteome - yes as transcriptome changes affect proteome. Phenotype - yes as different proteins may have differing phenotypic outcomes. Genome and exome - unaffected.

Question 43

Are epigenetic changes permanent/can be passed on?

Answer 43

Not permanent however can be passed on via mitosis and meiosis

Question 44

Discuss overview of nuclear transfer.

Answer 44

Somatic cell taken from parent. Egg cell taken from donor mother and enucleated, removing all genetic information. Somatic cell and enculeated egg cell are shocked to stimulate fertilisation and cell division.

Question 45

Define epimutations.

Answer 45

Mutations that occur that change the epigenome.

Question 46

Define consanguinity.

Answer 46

Marriage between individuals with the same ancestor.

Question 47

What is the degree of consanguinity?

Answer 47

The extent of relationship between the two individuals in question. Used to determine the average DNA shared between the two.

Question 48

Which familial relationship has the most DNA shares?

Answer 48

Identical twins/clones.