D3.2 Inheritance Flashcards
autosomal
gene located on one of the numbered or non sex chromosomes.
autosomal chromosome
numbered chromosomes in a karyogram ranged from smallest to largest
gregor mendel
cross bred different types of pea plants in monastery
300,000 plants over 8 years
large sample carefully planned, easily recognisable characteristics
parental generation (P)
first set of parents in a genetic cross. The parents genotypes are used to predict the genotype of their offspring
monohybrid cross
cross involving one pair of contrasting characteristics exhibited by homozygous parents
F1 generation
first finial generation
arises by crossing parents and when selfed or crossed via sibling crosses, produces the F2 generation
F2 generation
offspring produced by F1 generation
dominant allele
an allele that has the same effect on the phenotype whether it is present in the homozygous or heterozygous state
recessive allele
an allele that has an effect on the phenotype only when present in the homozygous state
punnet grid
diagram used to show and calculate all the combinations and frequencies of different genotypes and phenotypes among the offspring of a genetic cross
Mendells conclusions
- breeding factors controling characteristics
- 2 factors in each cell
- one factor from each parent
- factor can be separated and passed during reproduction
- factor tall is dominant and alternative to factor dwarf
law of segregation
pair of alleles segregate from each other during meiosis so that only one allele will be present in each gamete.
genotype
the combination of alleles inherited by an organism. genetic constitution of organism
homozygous
having 2 identical alleles of a gene
heterozygous
having 2 different alleles of a gene
phenotype
observable traits of an organism resulting from genotype and environmental factors
organisms can have the same __ but different __
phenotype
genotype
what can phenotype be determined by
genotype, environmental factors, interactions
eg. eyecolor and blood
recessive characteristic in phenotype
homozygous genotype
dominant characteristic
homozygous or heterozygous
may look alike but different genotypes
phenotypic plasticity
the capacity to develop traits suited to the environment experienced by an organism by varying patterns of gene expression
ex. exercise result
phenylkatonuria
a reccessive genetic condition caused by mutation in an autosomal gene that codes for the enzyme needed to convert phenylalanine to tryosine.
untreated infants with PKU
unusually light eye, skin and hair colour
high blood phenylalanine levels
disruptions in neurotransmiters such as dopamine
symptoms of PKU
seizures, abnormal muscle movements, tight muscles and tremors
can lead to sevre brain damage
cure for PKU
phenylalanine restricted diet
genotype for PKU
recessive
carrier
an individual that has one copy of a recessive allele that causes a genetic disease in individuals that are homozygous from this allele
single nucleotide polymorphisms
- represents a different in a single nucleotide
- can replace C with A
- many alleles can exist
- an individual can only inherit 2 alleles rather than the full number
blood groups
A B AB O
co dominant blood groups
I^A and I^B
co dominance
both alleles are expressed in a phenotype
incomplete dominance
where a dominant allele does not completely mask the effects of a recessive allele resulting in heterozygotes having an intermediate phenotype
what do sex chromosomes decide
gender
sex of offspring is determined by
the male
7th week of pregnancy
growth of genitalia if Y chromosome is present
Y chromosome codes for a protien called
testis determining factor TDF
testis determining factor functions
a molecular switch and initiates production of a low level of testosterone
in the absense of Y chromosome
ovary formed
under hormones from ovary develops female reproductive structures
sex linkage
special case of linkage occuring when a gene is located on a sex chromosome
usually the x chromosome
which chromosome is longer
X
alleles on Y are concerned with
male structures and functions
eg of recessive conditions
red green color blindness
haemophilia
haemophilia
blood doesnt clot normally
frequent and excessive bleeding
due to failure to produce proper particular blood protiens
genes for haemophilia are on which chromosome
X
recessive or dominant for haemophilia
recessive
haemophilia common in which gender
males
when is haemophilia fatal
fatal in uterus to women - abortion
analysis of pedigree charts
can be used to detect conditions due to dominant and recessive allels
dominant in pedigree charts
dominant - more and more in every generation
recessive in pedigree charts
recessive - infrequent and skips many generation
albinism
rare and recessive monohybrid inheritance
brachydactyly
fingers are very short
usually allele is dominant so tends ro occur in every generation
why is relative marraige prohibited mostly
probability is increased of child inheriting 2 copies of a harmful recessive allele rather than only one
polygenic inheritance
inheritance of phenotypic characters that are determined by the collective effects of several different genes
variation types
continuous and discontinuous
combined effect of all genes
continuous variation
continuous variation
continuous variation results in a range of phenotypes between two extremes; examples include height and weight
discontinuous variation
discontinuous variation results in a limited number of phenotypes with no intermediates; examples include ABO blood groups, seed shape in peas and seed colour in peas
human skin colour is what kind of variation
continuous distribution
human skin colour may be influenced by
environmental factors
characteristics are controlled by what
polygenes and show continuous variation
normal distribution curve
show variability but with value grouped symmetrically around a central value
skewed distribution
values reduce in frequency more rapidly on one side of the most frequently obtained value than on the other
what do box and whisker plots show
differences in the mean and range
