Chapter 20 Flashcards
somatic cells
body cells
chromosomes are made of ___ and _______.
DNA; protein
gene
segment of DNA located on a specific site on a chromosome that contains information for producing a particular protein.
Different versions of a gene
alleles
Two copies of the same allele of a gene
homozygous
Different alleles of a given gene
heterozygous
Dominant allele
when the effects of a certain allele can be detected regardless of whether an alternative allele is also present
Recessive allele
an allele whose effects are masked in the heterozygous condition
genotype
precise set of alleles a person possesses for a given trait
phenotype
the observable physical traits
law of segregation
for every gene in our chromosomes one of the alleles comes from our mother and one comes from our father
law of independent assortment
the mixture of alleles that came from the mother and alleles that came from the father is different in every gamete
Diagram used to predict the genetic makeup of the offspring of individuals of particular genotypes
Punnett square
monohybrid cross
a cross in which both parents are heterozygous for one trait of interest
dihybrid cross
a cross of individuals who are both heterozygous for two traits of interest
a chart showing the genetic connections between individuals in a family
pedigree
a Carrier
someone who displays the dominant phenotype but is heterozygous for a trait and can pass the recessive allele to descendants
complete dominance
a heterozygous individual exhibits the trait associated with the dominant allele but not the recessive allele
codominance
the effects of both alleles are apparent in the heterozygous phenotype ex: AB blood
incomplete dominance
the expression of a trait in a heterozygous individual is somewhere between the expression of the trait in a homozygous dominant and the expression of the trait in a homozygous recessive individual. ex: sickle cell trait
pleiotropy
one gene leading to many effects ex: sickle cell anemia
when 3 or more forms of a given allele exist
multiple alleles (in a population) ex: ABO blood types
polygenic inheritance
the involvement of two or more genes, often on different chromosomes, in producing a trait
20,000-25,000
human genes distributed among the 23 pairs of chromosomes
x-linked genes
genes located on the X chromosome. Most X-linked genes have no corresponding allele on the Y chromosome
sex influenced traits
the expression of certain autosomal genes influenced by the presence of sex hormones
breakage can be caused by
- chemicals
- radiation
- viruses
- crossing over
deletion
loss of a piece of chromosome
duplication
the addition of a piece of chromosome
