DAT bio Chapter 7. Heredity Flashcards
Genome
- all the DNA within a cell.
Gene
- sequence of DNA that codes for a trait.
locus
- location of a gene on a chromosome.
Plural is gene loci
allele
one variation of a gene
wild type allele
normal allele that is most
common in nature. Can turn into a mutant
allele
mutation
- heritable change in DNA
Genotype
Set of genes responsible for trait
Ex BB Bb bb
BB is brown eyes
Bb is blue eyes
Phenotype
observable traits that result from
a genotype.
Dominant alleles
- mask the expression of
recessive alleles. Typically represented by
uppercase letters (“A”)
Recessive alleles -
- only show up in a
phenotype if dominant alleles are not present.
Typically represented by lowercase letters (“a”).
Homologous pairs
two pieces of DNA within a diploid organism which carry the same genes, one from each parental source. In simpler terms, both of your parents provide a complete genome. Each parent provides the same 23 chromosomes, which encode the same genes
Heterozygous -
one dominant allele and one
recessive allele in its homologous pair
Homozygous -
- same allele in both homologs.
Can be homozygous dominant or
homozygous recessive.
Hemizygous
only one allele is present. For
example, men only have one X and one Y
chromosome (not homologous), which contain
hemizygous genes
Penetrance -
proportion of individuals who exhibit the phenotype of an allele for a given gene. Can be complete penetrance or
incomplete penetrance. As shown below, Bb
individuals all have brown eyes only when
there is complete penetrance (refers to the probability of a gene or trait being expressed. )
Expressivity
describes how well a certain phenotype is expressed? All of the
children of this couple have genotype Hh for
medium thick hair, but because of expressivity,
just how medium thick (or medium thin) the
hair is varies. (degree of how expressed one phenotype is)
Incomplete dominance
The dominant allele is not fully expressed when the recessive allele is around. will have an intermediate state. (Ex.
red x white = pink).
Codominance
heterozygous genotype
expresses both alleles. (Ex. red x white = red +
white spots).
Multiple alleles
n there are more
allele options than just two. (Ex. ABO blood typing
- A, B, O alleles)
Epistasis
One gene suppresses the expression of another gene
Ex. baldness gene covers up
the genes for hair color)
Pleiotropy
describes when one gene is
responsible for many traits. (Ex. cystic fibrosis is a
disease with many symptoms caused by a single
gene).
Polygenic inheritance
many genes are
responsible for one trait. This gives the trait
continuous variation. (Ex. height, a single trait
affected by many genes
Haploinsufficiency
when one copy of the
gene is lost or nonfunctional and the expression of
the remaining copy is not sufficient enough to
result in a normal phenotype. It can result in an
intermediate phenotype.
Haplosufficiency
describes when the remaining
copy of the gene is sufficient enough to result in a
normal phenotyp
Proto-oncogenes
e genes that can become
oncogenes (cancer-causing genes) due to
gain-of-function mutations. Gain-of-function
mutations can cause too much protein to be
made or production of an over-active protein;
Cancerous growth occurs as a result.
Proto-oncogenes are normally involved in cell cycle
contro
one hit hypothesis
states that a gain-of-function mutation in
one copy of the gene turns it into an oncogene. This is associated with proto oncogenes
Tumor-suppressor genes
(Anti oncogenes) genes that become
cancerous as a result of loss-of-function
mutations, because they are normally needed to
suppress cancerous growth
two hit
hypothesis
states that a loss-of-function
mutation in both copies of the gene are needed to
make it cause cancer. Thus, tumor-suppressor
genes are haplosufficient. This is associated with tuomr suppressor genes
Null alleles
come from mutations that cause the
alleles to lack normal function. Tumor-suppressor
genes have null alleles when they become
cancer-causing
p53
important tumor-suppressor gene
that is known as the guardian of the cell . It is
upregulated (increase its response to a substance) to prevent cells from becoming
cancerous.
p21
s another tumor-suppressor gene that
inhibits phosphorylation activity in order to
decrease rampant cell division.
Retinoblastoma gene (RB)
is a
tumor-suppressor gene that codes for a
retinoblastoma protein, which prevents
excessive cell growth during interphase
Gregor mendel proposed three laws
laws of dominance
law of segregation
law of independent assortment
laws of dominance
dominant alleles mask
the expression of recessive alleles. Mendel
studied plant height to come to this conclusion.
Law of segregation
homologous gene copies
separate during meiosis (specifically anaphase
I). Thus, Aa individuals will produce gametes
with “A” or “a” alleles
homologous gene copies
separate during meiosis (specifically anaphase
I). Thus, Aa individuals will produce gametes
with “A” or “a” alleles
homologous chromosomes line up
independently during metaphase I of meiosis
so that alleles separate randomly (this
increases genetic variability). Metaphase II is
different, during which sister chromatids are
pulled apart instead. The law of independent
assortment can produce 2
23 options (23 homologous chromosome pairs split).
