genetics (inheritance) Flashcards
what is a gene?
sequence of bases on a DNA molecule that codes for a protein, resulting in a characteristic
what is an allele?
different version of a gene- code for different versions of the same characteristic
what is a genotype?
genetic makeup of an organism- the alleles that it has
what is a phenotype?
expression of an organism’s genotype an its interaction with the environment- an organisms characteristics
what does dominant mean?
allele whose characteristics appears in the phenotype even when there’s only 1 copy
what does recessive mean?
allele whose characteristic appears in the phenotype if two copies are present
what does co dominant mean?
alleles that are both expressed in the phenotype- neither is recessive
what is a locus?
fixed position of a gene on a chromosome, allels of a gene are found at the same locus on each chromosome in a pair
what is a homozygote?
organism that carries two copies of the same allele
eg) BB or bb
what is a heterozygote?
organism that carries 2 different alleles
eg) Bb
what is a carrier?
person carrying an allele which is not expressed in the phenotype, but that can be passed onto the offspring
what chromosomes do females have?
2 X chromosomes
what chromosomes do males have?
an X and a Y chromosome
when is a characteristic sex linked?
the allele that codes for a characteristic is located on a sex chromosome
why are most genes on the sex chromosomes only carried on the X chromosome?
Y chromosome is smaller so carries fewer genes
why are males more likely to show recessive phenotypes for sex linked genes?
males only have one X chromosome
often only have 1 allele for sex linked genes
express this characteristic even if it is recessive
what is an autosome?
chromosome that isn’t a sex chromosome
why are genes on the same autosome linked?
as they are on the same autosome, they stay together in independent segregation
what happens when are two genes on an autosome more closely linked?
crossing over is less likely to split them up
what is epistasis?
when an allele of one gene masks the expression of the alleles of other genes
what is a species?
group of similar organisms that reproduce to give fertile offspring
what is a population?
group of organisms of the same species living in a particular area at a particular time
what is the gene pool?
complete range of alleles present in a population
what does the Hardy Weinberg principle predict?
that the frequencies of alleles in a population won’t change across generations
what conditions is the Hardy Weinberg principle true under?
large population no immigration no emigration no mutations no natural selection random mating
