1. Basic principles of genetics Flashcards
What is the difference between heredity and variation?
HEREDITY: offspring are similar to their parents
VARIATION: offspring are different from their parents (and each other)
What is the difference between genotype and phenotype?
Genotype genes that influence phenotype
Phenotype is what is expressed
What is the difference between eukaryotes and prokaryotes? (3)
Eukaryotes: Multicellular, has membrane bound nucleus, nuclear genes on multiple linear chromosomes
(Animals, plants, fungi and protists)
Prokaryotes: unicellular, NO nucleus, single circular chromosome
(Bacteria)
What are chromosomes made up of?
and what is this made up of?
Chromatin
Made up of DNA and histones (DNA wrapped around histones)
What is euchromatin?
loosely packed chromatin that can be readily transcribed
What is heterochromatin?
Condensed structure that does not allow expression of genes in that region
What are modifications to chromatin structure controlled by?
Controlled by addition of methyl and acetyl groups to the histone proteins
(characteristics are heritable)
How can gene activity be altered without changing the DNA sequence?
Modifications to chromatin structure
Describe the structure of linear chromosomes? (4)
Telomeres: structures at each end of linear chromosomes that protect them from degradation
Centromere: “specialised region that acts as a site for the binding of kinetochore proteins”
p arm (stands for “petite”) = shorter chromosome arm q arm (it’s the letter after p) = longer chromosome arm
What are the positions of protein coding regions known as?
Loci (Locus singular)
What is Cytogenetics?
The study of chromosomes
What is a technique used to study chromosomes?
What chemical is used to stain chromosomes and give unique banding pattern?
G-banding
Giemsa
What is a Karyotype
The chromosome complement of an individual
How many autosomes in a typical human Autosome?
1-22
What are the chromosome combinations for male and female?
XX = Female XY = Male
How many copies of each chromosome does a nucleus have?
2 (diploid)
What is mutation?
The process that produces a gene or a chromosome set differing from that of the wild type/The gene or chromosome set that results from such a process
What does wild type mean?
The form that predominates in nature / in a standard laboratory stock
What does Polyploidy mean?
Unusual number of chromosome sets
what does aneuploidy mean?
One or a few individual chromosomes extra / missing
What is:
Trisomy
Monosomy
Trisomy = 3 homologues instead of 2 Monosomy = 1 homologue instead of 2
What do these large-scale chromosomal rearrangements mean:
Deletions:
Inversions:
Translocations:
Deletions: part of the chromosome is missing
Inversions: part of the chromosome has been flipped
Translocations: part of the chromosome has been moved
What are sources of mutation?
Mistakes during replication:
- Point mutations
- Small insertions / deletions -> frameshifts
Genes interrupted by transposons
DNA breaks incorrectly repaired
What do these types of point mutations mean?
Silent:
Nonsense:
Missense:
Silent: no change to amino acid sequence
Nonsense: introduction of a stop codon into the gene
Missense: changes the amino acid sequence (this will have varying effects on protein function. “Null allele” = total loss of function)
What is an allele?
Different versions of a gene
What is an example of a genetic disease caused by rare, recessive, autosomal alleles?
Example: phenylketonuria
Caused by mutations in the gene for phenylalanine hydroxylase, involved in the metabolism of phenylalanine amino acid
Lack of functional enzyme causes harmful build-up if Phe in the body -> intellectual disability, seizures
But one functional copy is sufficient for metabolism
- PP homozygous dominant: normal Phe metabolism
- Pp heterozygous: normal Phe metabolism
- pp homozygous recessive: PKU
Where is most eukaryotic genetic material found?
Nuclear chromosomes
also some in mitochondria and chloroplasts
