mendelian genetics topic 9

genetics

scientific study of heredity

gene

DNA segment coding for specific protein

allele

different forms of a gene

genotype

combination of alleles

phenotype

physical trait

dominant alleles are what

always expressed

recessive alleles are what

only expressed if homozygous

what is phenotype result from

interaction of genotype and environment

probability

mathematical chance and event will occur

meiosis

cell division for sex cells

mutation

change in bases of DNA

natural selection

organisms with favorable traits survive and reproduce higher

evolution

accumulation of inherited traits by a population

punnett square

tool for predicting genetic probabilities

how many fombinations fo reach cross between parents

four

how did Mendel discover the basic principles of heredity

breeding pea plants

what was a key advantage to using pea plants for genetic study

they had lots of varieties

what do varietes lead to

distinct fetures or characters

what is each variant for a character called

trait

what are some other advantages of pea plants being used to study genetics

short germination, lots of offspring, can control mating (self polinate or cross polinated)

what did. cross polination lead to

mendel able to cross plants with different characteristics

what characteristics did mendel study about the peas

colour (green or yellow)

shape (round or wrinkled)

flower colour (purple or white)

height (tall or short)

what did he find of pea shaped when he crossed a round pea and a wrinkle pea

F1 gen was always heteozygous round, but when F1 was crossed F2 had a 3:1 ratio of round to wrinkle

what did principles did mendel come up with

law of dominance, segregation, independent assortment

law of dominance

dominant allele is always expressed

monohybrid cross

cross looking at one trait

what did mendel use in terms of breeding when crossing pea plants

true breeding

true breeding

plants that make offspring of same variety

hybridization

crossing 2 contrasting and true breeding varieties

what are true breeding parents called

P generation

The hybrid offspring of the P generation are called

F1 generation

what is it when F1 produced offspring

F2

stamens of plants

sperm producing organ

carpels of plants

egg producing organ

law of segregation

alleles seperate during gamete formation so offspring get one from each parent

what is the ratio when crossing a purple and whit flowers in the F1 and F2 generation

F1 all purple and F2 3:1 purple to white

when mendel called a heritable factor what do well call it now

gene

what happens when you cross monohybrid heterozygotes

3:1 ratio

first concept of mendels model

different gene versions account for variation in inherited characteristics

where does each gene live

specific of locus in chromosome

second concept of mendels model

organism inherited a copy for gene from each parent

Third concept of Mendel's model

if two alleles at locus differ, dominate allele determines appearance

Fourth concept of Mendel's model (law of segregation)

alleles for a heritable character sperate during gamete formatikon ending in different gamete

how many alleles do eggs or sperm recieve

one of two possible

was does segregation of alleles correspond to

distribution of homologs

how to determine the genotype of a dominant phenotype

testcross

testcross

breeding unknown with a homozygous recessive

what does a testcross tell you after completeing one

unknown is heterozygous if any offspring displace recessive trait

law of independent assortment

each pair of alleles separate independently during gamete formation

what was F1 offspring called

monohybrid

what happens when you cross 2 true breeding parents differing in 2 characteristics

dihybrids produced in F1

dihybrids

heterozygous for both characters

dihybrid cross used for

determine if two characters are transmitted together or seperatly

phenotypic ratio for dihybrid crosses

9 : 3 : 3 : 1 dominant both : dominant first, recessive second : recessive first, dominant second : recessive both

what does the law of independant assortment apply only to

genes on different chromosomes or far apart on same chromosomes

how are genes that are close to each other on the same chromosome inherited

together

multiplication rule

probability that 2 or more independent events will happen together is the product of individual probibilities

how can the probability in and F1 monohybrid cross be determined

using multiplication rule

what is the segregation in a heterozygous plant like

flipping a coin

what is the chance of in a little either being dominant or recessive

1/2 for each

What is the probability that an F2 plant from a mono hybrid cross will be homozygous recessive

rr is 1/2x1/2= 1/4

Addition rule

Probability that any one of two or more exclusive events will occur is calculated by adding together their individual probability

Probability that an F2 plant from a mono hybrid cross will be heterozygous

1/4+1/4=1/2

What can we apply multiplication edition rules to

Predicting outcomes of crossing multiple characters

What is a dihybrid cross equivalent to?

two or more monohybrid crosses

look at figure 14.un02

a

What is complete dominance

one allele masks the other in heterozygote

Incomplete dominance

hybrids with no dominant allele

codominance

Two dominant alleles affect phenotype in separate ways

What does incomplete dominant result in?

hybrid phenotype

Tay-Sachs disease

inherited disorder dysfunctional enzyme cause lipids to accumulate in brain

What is the Tay Sachs allele at the organism level?

Recessive

what is the phenotype of Tay-sachs disease at the biochemical level

Incompletely dominant

what are the alleles of Tay-Sachs disease at the molecular level

Codominant

How many babies are born with extra fingers or toes in Canada

1 our of 500

what is the allele for 5 digets

recessive

What is the three alleles that determine for the four blood groups?

I^A, I^B, i

what does the the enzyme encoded by I^A allele add

A carbohydrate

What does the enzyme encoded by the I^B allele add

B carbohydrate

what type of carb does the enzyme encoded by i allele add

none

Blood group a (phenotypes) genotype

I^A I^A or I^A I^i

Blood group B (phenotype) genotype

I^B I^B or I^B I^i

Blood group AB (phenotype) genotype

I^A I^B

Blood group O (phenotype) genotype

ii

What is pleiotropy

One gene affects many traits

What are pleiotropic allie's responsible for?

cystic fibrosis and sickle cell disease

What is epistasis?

Gene at one locus changes phenotypic expression of a gene at a second locus

What does Labrador retriever's coat colour depending on?

Two genes

look at example of epistasis figure 14.12

a

Quantitative characters

Characters that very in population along a continuum

What does quantitative variations indicate?

Polygenic inheritance

Polygenic inheritance

trait is controlled by multiple genes

What is an example of polygenic inheritance?

Skin colour

How many separate inherited jeans affect the darkness of skin

Three

Norm of reaction

range of phenotype a genotype can produce based on environment

multifactorial characters

genetic and environmental factors influence phenotype

What does an organism phenotype include?

Physical appearance, internal anatomy, physiology, behaviour

What does an organism phenotype reflect?

Genotype and unique environmental history

Why are humans not good for genetic research?

Generation time is too long, parents produced a few offspring, breeding experiments are unethical

Basic Mendelian genetics, endure as foundation of ______________________

Human genetics