17 inherited change Flashcards
what is a genotype
the genetic constitution of an organism, describes all the alleles that an organism has
what is a phenotype
the expression of the genes and it’s interaction with the environment
what is a gene
section of DNA on a chromosome coding for one or more polypeptides
what is a locus
the position of a gene on a DNA molecule
what is an allele
one of a number of alternative forms of a gene
what is monohybrid inheritance
the inheritance of a single gene
what does pure-breeding mean?
pure breeding produces offspring with the same phenotype as the parents, parents have to be homozygous
what is the theoretical ratio when the f1 generation are crossed with one another?
3(dominant) : 1(recessive)
what is the dominant allele?
an allele that is always expressed in the phenotype
what is the recessive allele?
an allele that is only expressed in the phenotype if it is homozygous
what is dihybrid inheritance?
the inheritance of two different genes on different chromosomes simultaneously
(RRGG, RRGg, RRgg, rrGG etc)
what is the theoretical ratio for a dihybrid cross?
9:3:3:1
what is codominance?
when both alleles are equally dominant, both expressed in the phenotype
what is multiple alleles?
more than two alleles for a single gene (only two can be present at any one time)
example of multiple alleles
blood groups could be group A, B or O
what is sex-linkage?
occurs when genes are on the X chromosomes
what chromosomes do males and females have
male = XY female = XX
what is autosomal linkage?
occurs when two genes are on the same chromosome
what is the chi-squared test used for in genetics?
to see if the difference between the observed value and the expected value is significant or nor
why does autosomal linkage reduce variation?
pairs of alleles are inherited together
why do some males suffer from sex-linked diseases?
their Y chromosomes is missing some genes that are carried on their X chromosome, so some recessive alleles on the X chromosome are expressed alone, giving the disease phenotype
what is homozygous?
a pair of homologous chromosomes carrying the same alleles for a single gene
what is heterozygous?
a pair of homologous chromosomes carrying two different alleles for a single gene
what is epistasis?
when one gene modifies or masks the expression of a different gene
