Genes and Patterns of Inheritence Flashcards
Genes and Inheritance
What plant did Gregor Mendel use
Garden pea
Genes and Inheritance
Traits Mendel observed
Flower colour
Flower position
Seed colour
Seed shape
Pod shape
Pod colour
Height
Genes and Inheritance
Single factor cross
When an experimenter looks at only one trait
Genes and Inheritance
P generation
True breeding parents
Genes and Inheritance
F1 generation
Offspring of P cross
Genes and Inheritance
P cross
When you cross true bredding parents (P generation)
Genes and Inheritance
F2 generation
Result of allowing F1 generation to self fertilise
Genes and Inheritance
Dominant trait
Displayed trait
Genes and Inheritance
Recessive trait
Trait that is masked by the dominant trait
Genes and Inheritance
Gene
Sequence of DNA
Specific area of a specific chromosome
Codes for one of an organisms traits
Genes and Inheritance
Allele
Variation of a gene
Every individual has 2 alleles for every trait
Can be dominant or recessive
Genes and Inheritance
Medel’s Law of segregation
2 copies of a gene seperate from each other during the transmission from parent to offspring
Genes and Inheritance
Segregation of alleles
The two copies of allels carried by the parent seperate from each other
Each sperm/egg carries only 1 allele
Genes and Inheritance
The ratio of traits Medel found in F1
3:1
Genes and Inheritance
Genotype
Genetic composition of an individual
Homozygous or heterozygous
Genes and Inheritance
Homozygous
Carry two alleles for a gene that are the identical
Genes and Inheritance
Heterzygous
Carry two alleles for a gene that are different
Genes and Inheritance
Phenotype
Characteristics of an organism resulting from the expression of its genes
Genes and Inheritance
Method for predicting the outcome of crosses
Punnett square
Genes and Inheritance
Test cross
Used to determine an individuals genotype
Cross with a homozygous recessive individual
Genes and Inheritance
Test cross results in offspring that all have the dominant trait
Homozygous for the dominant trait
Genes and Inheritance
Test cross results in offspring where half have the dominant trait and half have the recessive trait
Heterozygous
Genes and Inheritance
Test cross results in offspring that all have the recessive trait
Homozygous for the recessive trait
Genes and Inheritance
Two factor cross
Follow inheritance of 2 different traits
Can either be linked or independant
Genes and Inheritance
Two-factor cross results in a 3:1 ratio of offspring characteristics. How are the genes assorted
Linked assortment
Genes and Inheritance
Two-factor cross results in a 9:3:3:1 ratio of offspring characteristics. How are the genes assorted
Independant assortment
Genes and Inheritance
Law of independant assortment
Alleles of different genes sort independantly of each other during gamete formation
Genes and Inheritance
Locus
Physical location of a gene on a chromosome
Genes and Inheritance
Wild type allele
Prevelant allele in a population
Encodes a protein made in the proper amount and functions normally
Genes and Inheritance
Mutant alleles
Altered by a mutation
Tend to be rare in natural populations
Almost always unable to express a funtional protein
Genes and Inheritance
Simple dominance
Recessive allele doesn’t affect the phenotype of a heterozygous individual
Dominant allele masks it
Genes and Inheritance
Reasons for Mendel using the plant he did
Many different characteristics/traits
Self-fertilising
Easy to make crosses with
Genes and Inheritance
Imcomplete dominance
Heterzygous offspring can show an intemdiate trait to the phenotypes of parents
Neither allele is dominant
50% of normal protein isn’t enough
Genes and Inheritance
Codominance
Heterzygote express both alleles simultaneously
Genes and Inheritance
Pleitropy
Mutation to a single gene can have multiple effects to an individuals phenotype
Genes and Inheritance
Plant used to discover incomplete dominance
Four-o’clock plant
Genes and Inheritance
X linked genes and disorders
Males hemizygous for X-linked genes
X-linked recessive traits more likely in males
Genes and Inheritance
Hemizygous
Only one copy of gene is present
Genes and Inheritance
X-linked genes
Genes found on the X chromosome but not the Y
Genes and Inheritance
Norm of reactions
Effects of environmental variation of phenotype
For example, plants in better soil grow bigger
Genes and Inheritance
Gene interaction
When a single charecteristic is controlled by 2 or more genes
Genes and Inheritance
Epistasis
Gene interactions
When the alleles of one gene can mask the expression of alleles from another gene
Often because 2 or more different proteins involved in a single cellular function
Genes and Inheritance
Bateson and Punnett
Early 1900s
Crossed 2 varieties of white flowered pea
F1 had all purple flowers - Unexpected
F2 had a 9:7 ratio of purple:white flowers
Concluded must be 2 genes involved in flower colour
Genes and Inheritance
Discrete traits
Clearly defined phenotypic varients
One or the other trait
Genes and Inheritance
Quantitative traits
Show contineous variation over a range of phenotypes
Usually polygenic
Environment plays a role
Genes and Inheritance
Example of discrete trait
White or purple flowers
Red or white eyes
Genes and Inheritance
Examples of quantitative traits
Height
Hair colour
Skin colour
Number of apples on a tree
Genes and Inheritance
Polygenic
Several or many genes contribute to the outcome of the trait
Many contribute in an additive way
Genes and Inheritance
Gene linkage
When 2 genes are close on the same chromosome
Tend to be transmitted as a single unit
Don’t tend to follow the law of independant assortment
Genes and Inheritance
Recombinants
Normally small number of total offspring
Don’t have the traits of parental generation
Genes and Inheritance
Nonrecombinants
Combination of traits has not changed from the parental generation
Genes and Inheritance
Stage of meiosis where chromsomes can be echanged
Crossing over
Genes and Inheritance
What effects the likelihood of crossing over
Distance between two genes
More likely in genes that are far apart
Genes and Inheritance
Recombination frequency
Frequency of crossing over between two genes
Used to work out the distance between them
Genes and Inheritance
Gentic linkage mapping/gene mapping/chromosome mapping
Used to determine linear order of genes that are linked to each other along the same chromosome
Genes and Inheritance
Genetic map
Chart that shows relative locations of genes on a chromosome
Estimated by how likely a crossover will occur between linked genes
Genes and Inheritance
Map units
Units of distance between two genes
Equivalent to 1% recombination frequency
Genes and Inheritance
Test crosses and recombination frequency
Do a two-test cross
If this produces lots of recombinants you can conclude that the two genes are far apart
Ver few recombinants - close together
Genes and Inheritance
What can you conclude from a test cross where there are a lot of recombinant offspring
The genes in question are far apart on the chromosome
Genes and Inheritance
Map distance =
Number of recombinants/\total number of offspring
Multiply answer by 100
