BIO A01 - genomes, mutations and genetic variation (Module 3 L10)

genomes, mutations and genetic variation, course: BIO A01, Lecture 10

GENOMES

A genome is the genetic material of a cell, organism, organelle, or
virus, and its sequence is the order of bases along the DNA or (in
some viruses) RNA.
A genome is the genetic material transmitted from parents to
offspring

does large genome = more complex organism

no

Mutation =

any heritable change in the genetic material

Generally, mutations tend to occur spontaneously and at
random

germ-line mutations;

Mutations can take place in reproductive cells

somatic mutations

mutation in non-reproductive cells

Had the mutation arisen spontaneously in the bacteria and was
already present prior to plating on selection media?

-mutations arise without regard for the needs of the organism

• Did the mutation arise after and in response to being plated on the
selection media?

-the needs of the organism do have some type of impact on
the process of mutati

POINT MUTATIONS –

CHNAGES IN A
SINGLE NUCLEOTIDE

results of point mutation

synonymous

nonsynonymous

synonymous mutation

doesnt change amino acid

nonsynonymous

changes amino acid

nonsense mutation

Definition: A type of mutation that changes a codon to a stop codon, resulting in a shorter, nonfunctional protein.

insertion

Insertion is a type of mutation involving the addition of one or more nucleotides into a DNA sequence.

deletion

Deletion is a mutation involving the loss of one or more nucleotides from a DNA sequence.

frameshift mutation

A mutation caused by insertions or deletions in a DNA sequence that alters the reading frame of the genetic code.

Genetic variation:

Genetic variation: genetic differences that exist among individuals in a
population at a particular point in time
Genetic variation = variety of different genotypes = variety of different phenotypes

pOLYMORPHISMS

• Mutation is the ultimate source of variation in genotypes
• Common genetic differences that exist between individuals = polymorphisms
- differences are typically seen at single nucleotides
= single nucleotide polymorphisms (SNPs

VARIABLE NUMBER OF TANDEM
REPEATS (VNTR)

Different individuals may have different numbers
of repeated sequences in particular locations on
their chromosomes

COMPLEX TRAITS

Complex traits such as height and blood pressure are called
quantitative traits = measure along a continuum with only small
intervals between similar individuals.

COMPLEX TRAITS INFLUENCED BY
THE ENVIRONMENT

Environmental factors can affect
the variation in phenotype
between individuals (e.g.,
amount of sunlight, water,
wind, nutrients).
Environmental risk factors exist
for several common human
diseases
e.g., high salt intake for high
blood pressure

COMPLEX TRAITS INFLUENCED BY MULTIPLE GENES

Complex traits are influenced by multiple genes working together. These traits exhibit continuous variation in phenotypes, making them difficult to predict. Examples include height, skin color, and susceptibility to diseases.

GENOTYPE-BY-ENVIRONMENT INTERACTIONS

no 1 genotype = ideal across diff env

no 1 env = ideal across diff genotypes

slope if env based

0

slope if gentic based

1

Heritability

he proportion of the variation between
individuals that can be attributed to genes alone

Concordance

Concordance is the
percentage of cases in which
both members of a twin pair
show a trait when it is
known that at least one twin
shows the trait.
• The difference in the
concordance between MZ
and DZ twins is a measure
of the relative importance
of genotype.

Genes show
pleiotropy

single gene
has multiple
effects

PERSONALIZED
MEDICINE

• The multiple genetic and environmental factors affecting complex traits
imply that different people can have the same disease for different reasons.
• Personalized medicine = identify the patient’s genotype and tailor the
treatment to the individual’s genetic risk factors and lifestyle
-Match the treatment to the patient, not the disease