Genetics Flashcards
Abiotic Factor
Non-living environmental factor, such as temperature, pH, humidity, carbon dioxide concentration
Acetylation
Addition of an acetyl group COCH3
One of several histone modifications that can control transcription
Addition
Type of gene mutation in which a base is added, causing a frame shift in one direction so that many codons are changed
Adult stem cell
Multipotent cells found only in specific adult tissues, including bone marrow, that can only nature into limited number of cell types
Autosome
Any chronosome that is not a sex-determining chromosome
In meiosis, why do X and Y chromosomes pair up differently
Don’t form a typical bivalent
X and Y are different sizes and shapes and lengths
Chromatids are unable to line up and firm bivalent because most of the length is not homologous and short pairing region
Gene
A section of DNA that codes for a specific protein
Genotype
The genetic constitution of an organism
All the alleles it possesses
Genepool
All the alleles within an interbreeding population at a specific time
Population
All the individuals of the same species that occupy the same area at the same time
Phenotype
The expression of observable characteristics of an organisms genotype and its interaction with its environment
Locus
The position of a gene on a chromosome
Different alleles for same gene are found in same loci on homologous chromosomes
Homozygous
Most organisms are diploid
Having two copies of the same allele of a gene
Heterozygous
Most organisms are diploid
Having two different copies of an allele of a gene
Usually phenotype isn’t a mixture of them both and one is expressed in it only
Dominant allele
Always expressed in the phenotype regardless of being homozygous or heterozygous
Recessive allele
Only expressed in the phenotype if genotype is homozygous
Codominant allele
Equally expressed within the phenotype
Diploid
Adult stem cells (somatic) are usually diploid
Two copies of a gene
Can be same of different (homozygous or heterozygous)
Genetic cross
Diagrams that show the way in which alleles are inherited from one generation to the next
Allele represented by a letter
Dominant = Uppercase
Recessive = Lowercase
Expected phenotype offspring for monohybrid (heterozygous parents)
3:1
Expected phenotype offspring for codominance (heterozygous parents)
1:2:1
Expected phenotype offspring for dihybrid (heterozygous parents)
9:3:3:1
Expected phenotype offspring for epistasis (heterozygous parents)
9:4:3
15:1
9:7
Ratio adds up to 16 but not 9:3:3:1
Expected phenotype offspring for autosomal linkage (heterozygous parents)
3:1 if there is no crossing over
4:4:1:1 due to formation of recombinant alleles
4 phenotypes not showing 9:3:3:1
Haploid
Only one copy of a gene
Gametes produced from meiosis to prepare for fertilisation in sexual reproduction
Hardy Weinberg equations
P+q=1
P2+2Pq+q2=1
P+q=1
P?
q?
Frequency of the dominant allele
Frequency of the recessive allele
P2+2Pq+q2=1
P2?
2Pq?
q2?
Frequency of the homozygous dominant individuals
Frequency of the heterozygous individuals
Frequency of the homozygous recessive individuals
Hardy Weinberg principle predicts…
The allelic frequencies of a particular gene from one generation to the next will remain constant
Providing there is no migration, gene mutations or selection
Hardy Weinberg assumes…
No migration (isolated gene pool no gene flow in/out) No random gene mutations No selection for or against allele
Population size is large
Mating/fertilisation should be random
Monohybrid Inheritance
Inheritance of a single gene that determines a single characteristic
Order when working through breeding individuals
Phenotype Genotype Gametes circles Cross Genotypes Genotype ratio Phenotypes Phenotype ratio
Codominance (monohybrid)
No dominant/recessive relationship
Heterozygous individuals produce an intermediate phenotype
C^R and C^W
Multiple alleles (monohybrid)
Several alleles in the population like black brown ginger blonde
H^b H^bl H^g etc
Sex linked rules for dads and daughters to prove its not sex linked
If a daughter is affected
And father is not
And it is recessive
It is not sex linked
Sex linked rules for mothers and sons to prove it is not sex linked
If son is affected
And mother is not
And it is dominant
Then it is not sex linked
Crossing over
Prophase 1
Bivalent forms between 2 homologous chromosomes
Chiasmata and equal lengths of non sister chromatids exchanged
New recombinant alleles formed
5 to 10% only
Genetic linkage
Tendency of genes located close to each other on the same chromosome to be inherited together during meiosis and appear in the same gamete
Epistasis
Interaction between two genes where one allele affects/influences the expression of another
Can lead to graduation of a phenotype
Can occur in metabolic pathways
Why isn’t the expected phenotypic ratio always observed
Random fertilisation of gametes Small sample size Linked genes, sex linkage Epistasis Lethal genotypes
