ch 7- heredity Flashcards
locus
locaition of a gene on a chromosome
gene
sequence of DNA that codes for a trait
allele
variation of a gene
found at the same loci on both chromosomes in a homologous pair
wild type allele
normal allele most common in nature
mutation
HERITABLE change in DNA
hemizygous
only one allele is present
example- men only have one X and one Y chromosome which contain hemizygous genes
penetrance
proportion of individuals who have the phenotype associated with a specific allele
complete penetrance- the gene for a trait is expressed in all the population who have the gene
incomplete penetrance- the genetic trait is expressed in only part of the population
expressivity
the degree of a certain phenotype for a given genotype
every kid has curly hair, but the curls look different
incomplete dominance
heterozygous will have intemediate state
ex. red and white make pink
example of multiple alleles
there are more than two allele options- ex, blood typing
epistasis
one gene affects the expression of a different gene
ex baldness covers the gene for the colour of hair
pleitoropy
one gene is responsible for many traits
ex. cystic fibrosis gene rewsponsible for many symptoms
polygenic inheritance
many genes responsible for one trait
gives the trait continous variation
haploinsufficiency
one copy of the gene is lost and the expression of the remaining copy is not sufficient enough to have normal phenotype
results in intermediate phenotype
proto oncogenes
can become oncogenes due to GAIN OF FUNCTION mutations
follow one hit hypothesis
gain of function mutations
cause too much protein to be made or production of an over active protein leading to cancerous growth
one hit hypothesis
gain of function mutation in one copy of the gene turns it into an oncogene
tumor supressor genes
become cancerous due to loss of function mutations
two hit hypothesis
haplosufficient !!
two hit hypothesis
loss of function mutation is needed in both copies of the gene to make it cancerous
null alleles
come from mutations that lead to a lack of normal function in alleles - tumor supressor genes have null alleles when they become cancer causing
p53
tumor supressor gene that is known as the guardian of the cell
upregulated to prevent cells from becoming cancerous
p21
another tumor supressor gene that inhibits phosphorylation activity to decrease rampant cell division
retinoblastoma gene
tumor supressor gene that codes for retinoblastoma protein
prevents excessive cell growth during interphase
what are the three laws of gregor mendel
law of dominance
law of segregation
law of independent assortment
law of segregation
homologous gene copies separate during meiosis anaphase I
Aa individual produces gametes with A and a alleles
law of independent assortment
Homologous chromosomes line up independently during metaphase I of meiosis so that alleles separate randomly (this increases genetic variability).
The law of independent assortment can produce 2^23 options (23 homologous chromosome pairs split).
non disjunction
improper segragatino of chromosome pairs during anaphase
single nondisjunction of chromosomes during meiosis i
single nondisjunction of chromosomes during meiosis II
single nondisjunction of chromosomes during mitosis
single nondisjunction of chromosomes during meiosis i
24, 24, 22, 22
single nondisjunction of chromosomes during meiosis II
24, 22, 23, 23
single non disjunction in mitosis
47, 45
aneuploidy
abnormal number of chromosomes in the daughter cell which leads to trisomy or monosomy after fertilization
disomy- normal diploid cell
down syndrome
trisomy of the 21st chromosome
each diploid cell have 47 chromosomes total
turner syndrome
monosomy of the X chromosome in females
each diploid cell has 45 chromosomes
physical abnormalities and sterility
klinefelters syndrome
trisomy of the sex chromosomes in males giving XXY and 47 chromosomes
intelectual issues
physical issues
and reproductive issues
trisomy x
trisomy of x chromosomes in females
learning disabilities and attention issues
test cross
pairs an individual of unkown genotype with one that is homozygous recessive
where can mendels three laws be studied
in the f2 generation
dihybrid cross
examines the inheritance of two genes on separate chromosomes
females and males on pedigree charts
females- cicles
males- square
recombinant vs non recombinant gametes
recombinant- receive gentically unique chromatids
nonrecombinant- receive parental chromatids- did not undergo crossing over
linked genes
found close tog on the same chromosome
deduce relative distance between genes by looking at recombination frequencies
map unit
1% of recombination bw two genes (1cM- centrogram)
recombination frequency of _ means genes are linked
less than 50% means they are linked
when genes are perfectly linked, they have a recombination frequency of
0
linkage maps
tables used to determine the probability of inheritance
use map units to infer distance between genes on a chromosome
haplotype
group of genes usually inherited tog bc they are close to each other on the chromosome
epigenetics and twins
cause monoxygous twins to have different susceptibilities to the same disease
genomic imprinting
genes expressed depending on parental origin - influenced by epigenetic factors
only one copy of gene in individual expressed- either from mom or dad and the other is expressed
diff from sex linked triats bc they come from autosomal chromosomes (non sex chromosomes)
histone methylation vs DNA methylation
histone methylation- either upregulate or downregulate
DNA methylation- supresses gene expression - prevent transcription factors from binding
x linked dominiant
Dominant inheritance on the
X chromosome. Any offspring (male or female) that receive the affected allele will end up with the disorder.
x linked recessive
Recessive inheritance on the X chromosome. For males, only one affected allele is needed to cause the disorder. For females, two affected alleles are needed to cause the disorder because females have two X chromosomes. Hemophilia and color-blindness are examples of X-linked recessive conditions.
y linked
Inheritance on the Y chromosome. Can
only be passed from father to son. Will always be expressed whether it is dominant or recessive because males only have one Y chromosome.
x inactivation
process by which one of females x chromosomes is inactivated forming a Barr body and preventing excess transcription
female carrier can become affected for a disease if her unaffected x vhromosome with wild type allele is inactivated
