Unit 9-Patterns of Inheritance Flashcards
Mendelian Genetics
made the DNA model hypothesis experimental design found true breeding lines used large amounts of DNA statistical analysis
define heredity
the transmission of traits from one generation to the next
define genetics
the scientific study of heredity
began by Mendel
what is a character
a heritable feature that varies among individuals such as flower colour
what is a trait
each variant for a character such as purple OR white flowers
different forms of a gene
what is a phenotype
the distinguish between an organisms physical traits (what you can see)
outward expression of the characteristic
what is a genotype
its genetic makeup, what it has but may not show
the alleles present
what is a gene
DNA encoding for a product or characteristic
what is an allele
the alternative versions of a gene
form of a gene
has two copies one from each parent
some are dominant and some are recessive
what Is a dominant allele mean
that is what is expressed
it masks the expression of another allele
does not mean the normal or common trait
what is a recessive allele mean
has no noticeable effect on the organisms appearance
what is homozygous dominant
when the offspring receives two identical alleles for a gene that are dominant BB
what is homozygous recessive
when the offspring receives two identical alleles for a gene that are recessive bb
what is a heterozygous
an organism that has two different alleles for a gene
carriers for the recessive trait
what is self fertilization
sperm carrying pollen grains released from the stamens and land on the egg containing carpel
what is cross fertilization
fertilization of one plant by pollen from a different plant
what is true breeding
varieties for which self fertilization produced offspring all identical to the parent
what is a hybrid
the offspring of two different varieties
what are the multiple generations of mendels studies
the P generation - parental - true breeding plants the F1 generation - the parental hybrid offspring the F2 generation - when the F1 plants are self fertilized each other and their offspring is the F2gen
what is a monohybrid cross
a cross involving one trait
between the true breeding P generation
what is a dihybrid cross
what is a trihybrid cross
a cross involving two traits
true breeding between the P generation
a tri means three traits
Mendel’s experiment
P generation (Purple x White) gives F1 generation (All purple) gives F2 generation (white color comes back 3:1)
what are punnet squares
a diagram that shows the four possible combinations of alleles that could occur when these gametes combine
define law of segregation
a sperm or egg carries only one allele for each inherited character because allele pairs separate (segregate) from each other during the production of gametes
separate in meiosis
define the law of independent assortment
each pair of alleles segregates (assorts) independently of other pairs of alleles during gamete formation
the inheritance of one character has no effect on the inheritance of another
what is a test cross
used to determine the genotype of the unknown parent
what are wild type traits
those prevailing in nature and are not necessarily specified by dominant alleles
what are some dominant character traits that are inherited in humans
windows peak
cleft chin
hitchhikers thumb
what are some recessive disorders inherited in humans
sickle cell anemia
cystic fibrosis
what are some dominant disorders inherited in humans
achondroplasia
huntingtons disease
what is sickle cell anemia
no dominant allele (codominance)
no intermediate phenotype has both
what is incomplete dominance
does not support the blending hypothesis
the appearance of F1 hybrids falls between the phenotypes of the two parental varieties
NO DOMINANT ALLELE
ie) human hair texture or snapdragon flowers
what is complete dominance
the dominant allele has the same phenotypic effect whether present in one or two copies
multiple alleles
more then two allelic forms of a given gene (diploid)
what is an example of multiple alleles
human ABO blood types
both IA and IB are dominant
define codominance
the blood example IA and IB are co-dominant
both alleles are expressed in heterozygous individuals who have type AB blood
neither allele masks the presence of the other
different then incomplete dominance
define polygenic inheritance
the additive effects of two or more genes on a single phenotypic character
multiple genes affect a single trait
what are some examples of polygenetic traits
human skin pigmentation
has three melanin genes
define the chromosome theory of inheritance
that genes occupy specific loci (positions) on chromosomes and it is the chromosomes that undergo segregation and independent assortment during meiosis
what do the chromosomes affect in inheritance
law of segregation
law of independent assortment
linked genes
sex linked genes
what are lethal dominant genes
most genetic disorders
are homozygous recessive
ie) achondroplasia
what is achondroplasia
partial lethal dominant condition
heterozygous survive
homozygous dominant die
the mutation affects long bones of the heterozygous that survive
is it possible to have a complete dominant condition what is an example
very rare because the homozygous typically die
ie) huntingtons disease
explain huntingtons disease
causes neuron degeneration
abnormal movements and mental deterioration
symptoms appear at 35-45
define linked genes
genes located close together on the same chromosome tend to be inherited together
does linked genes follow Mendel’s law of independent assortment
NO
explain crossing over
the recombination of DNA
occurs during prophase 1 when the homologous pair up to form tetrads and cross over at the chiasma
do linked genes always assort together
yes without crossing over
what happens to the linked genes after crossing over
it is random and it recombinants
the closer the genes the further they will move apart ?
what is the linkage map
a diagram used to notice the relative gene locations
what are the different types of sex chromosomes to determine sex
humans or fruit flies - XX OR XY birds - ZZ OR ZW grasshoppers - XX OR X0 bees and wasps - 2N OR 1N
sex linked inheritance
occurs on the X chromosome
unique inheritance pattern
male pattern baldness
colour blindness
Allele frequencies p and q
p = the Dominant frequency
q = the recessive frequency
p + q = 1
What are the four conditions of studying populations that are not evolving
1) mutations - change allele frequencies
2) mating must be random neither phenotype has an advantage
3) small populations are prone to random changes so there must be a large population
4) isolated population - no one leaves and no one enters
