Mendelian Genetics Flashcards
what are alleles
- each variation of a gene, which encodes for a slightly different protein
- are in pairs and represented by 2 letters
what is a phenotype
the physical appearance due to a specific gene
what is a genotype
genes(alleles) possessed by indivudals
what is homozygous
an individual who has 2 identical alleles of a gene
what is heterozygous
an individual who has 2 different alleles of a gene
what is a dominant allele
A ‘strong’ allele which dominates over the other, causing that phenotype to emerge
what is a recessive allele
A ‘weak’ allele which is dominated by the dominant allele, thus its phenotype not being present
what are co-dominant alleles
alleles which are equally strong, thus creating mixtures of the phenotype of each allele in an individual
what is a locus
the physical position of a gene on a chromosome
what is a carrier
an individual who has a recessive allele that does not affect their phenotype, yet still has that allele present
what is a punnet grid +use
- it is a diagram that shows all the possible combinations of alleles for a particular trait
- used to predict the outcome of genetic crosses (inheritance)
who was Mendel
- austrian priest who investigated inheritance
- used pea plants to experiment
- not first person to do this work, first person to count and quantify genetic crosses
what are mono-hyrbrid crosses
crossing pure bred individuals with a different allele for a specific trait
what is a di-hybrid cross
a cross between two individuals that differ with two traits
What is Mendel’s third law (law of independent assortment)
- genes do not influence each other with regard to sorting alleles into gametes
- Genes which are located on different chromosomes segregate independently from one another during gamete formation
-ALLELES OF GENES ON NON-HOMOLOGOUS CHROMOSOMES ASSORT INDEPDENTLY DURING MEIOSIS
what are linked genes
genes that are located very close to one another on the same chromosome
-don’t follow Mendel’s second law, crossing over less likely to occur
what is Mendel’s first law (law of dominance)
In a cross of parents that are pure for contrasting traits, only one form of the trait will appear in the next generation. Offspring that are hybrid for a trait will have only the dominant trait in the phenotype.
what is Mendel’s second law (law of segregation)
During the formation of gametes (eggs or sperm), the two alleles responsible for a trait separate from each other. Alleles for a trait are then “recombined” at fertilization, producing the genotype for the traits of the offspring.
what is an example of co-dominance + both multiple alleles
blood type
what are autosomal sex chromosomes
22 pairs of autosomes, 1 pair of sex chromosomes
-sex chromosomes control male (XY) and female (XX)
-
what determines the sex of the offspring, the genetic makeup of the sperm or the genetic makeup of the egg
the genetic makeup of the sperm (X or Y) determine the gender
what is sex-linkage
- genes carried by sex chromosomes
- sex-linkage is the assosiation of a trait with gender (gene controls traits on a sex chromosome)
where do males and females recieve x-linked genes from
- male from mom (1copy): one allele for a particular trait
- female from both parents (2 copies)
what are the symbols for sex-linked genes
- XA=normal allele
- Xa= recessive allele
what are heterozygous females with X-linked disorders called
carriers
what are examples of sex-linkage disorders
- hemophilia
- color blindness
what is hemophilia
- sex linked
- woman is carrier
- recessive
- 50% of sons inherit disease, 50% of daughters carriers
- daughters of sons will be carriers, sons unaffected (only girls receive X-chromosome)
what is color blindness
-inability to see certain colors
-common: inability to see red and green
-x-linked disorder
-ressive
-males usually have it
-
what are autosomal disorders
- disorders which affect males and females equally
- dominant and recessive types
- takes only 1 copy of gene to cause disorder
- if child inherits diesease, at least one parent has it
example of autosomal disorder
-cystic fibrosis
what is a pedigree
-a chart of genetic history of family over generations
why is a pedigree chart used
- to deduce is trait is dominant or recessive, inherited, sexlinked or autosomal
- to deduce the genotype of indivudals
- to deduce the probability of a child having a condition
tips to read a pedigree chart
- if most males have it, its X-linked
- if its a 50/50 ratio of male and women; autosomal
- if the disorder is autosomal dominant, one of the parents must have disorder
- if autosomal recessive, none of the parents has to have the disorder to be heterozygous
