GENETICS NOTES CHAPTER 11 Introduction to Genetics

GENETICS NOTES_CHAPTER 11 Introduction to Genetics/More on Genetics-chapters13,14

I.The work of Gregor Mendel

•______=The scientific study of heredity.

Mendel’s Pea Plants
Austrian monk whose statistical work w/ pea plants yielded a greater understanding of biological inheritance
He knew each flower produces pollen,containing the male reproductive cells-sperm and female portion produces egg cells.During sexual reproduction,male and female cell join in ______-making a new cell that develops into an embryo
Pea plants self-pollinating
He started w/ true-breeding plants-meaning that if they are allowed to self-pollinate,they make offspring ______to themselves.
1 group ____ plants
1 group ______
1 made only ______seed
1 made ______seeds

****Mendel wanted to produce seeds from male and female reproductive cells from 2 different plants,preventing self-pollination by cross-pollination,with 2 different plants as parents….This allowed him to cross- breed characteristics

Genes & Dominance
Mendel studied different characteristics.
These characteristics are called ______-such as seed or flower color or height in humans
Studied 7 traits-see p.264-and he studied the offspring
The offspring are called F1(“first filial”…Filius and filia are Latin words for son and daughter)
______are the offspring of crosses of parents w/different traits.

****Mendel expected characteristics to blend-like red+white=pink-This was not the outcome

•2 conclusions:

–1) biological inheritance is determined by factors carried by one generation to another.we now call these chemical factors that determine traits______.

•Different forms of a gene are called ______

–2) The Principle of Dominance states some alleles are ______and some are recessive

•Alleles occur in pairs and only one allele w/ a certain trait needs to be present for a ______trait

•2 alleles of that trait must be present for ______traits.

•Tall plants were dominant and short recessive

C.Segregation

Mendel wondered if the recessive alleles had disappeared or were they still present in the F1 plants .He allowed all 7 kinds of F1 hybrids to produce an F2 generation by self-pollination

•F1 cross-recessive traits reappeared(~ ¼ F2 showed recessive trait)

•Mendel said the alleles for tall and short segregated(separated) during formation of sex cells

•Each gamete (Sex cell) carries a single copy of each gene

•F1 produces 2 types of gametes-one has short allele and one has tall allele.

•______letter stands for dominant allele and lower case letter for ______.example:Tt T stands for tall and lower case for short.

PROBABILITY AND PUNNETT SQUARES

–Likelihood for occurrence for a particular event is ______

–PAST OUTCOMES DO NOT AFFECT FUTURE OUTCOMES

–Probability is used to determine genetic occurrences using a diagram called a ______-which can predict and compare genetic variations that will result from a cross.

–______means the organism has the same 2 alleles for a trait---TT—also called true-breeding

–______means the organism has 2 different alleles for a certain trait---Tt-also called hybrid.

–______is the observed physical trait----example:tallness or shortness

–______=genetic makeup or actual alleles----example:TT or Tt

T t

T
t

Genotypes______

Phenotypes______

–Each offspring will have the same probability of a genotype and phenotype because each is ______or a single occurrence

–Larger the # of offspring ,the closer to______

III. Mendelian genetics

•Mendel wondered if the segregation of one pr of alleles affected another(?)

•A) Independent Assortment

–To answer his questions ,he performed a ______.

•1)Two-Factor Cross F1

–Crossed truebreeders w/ only round yellow peas (genotype RRYY) x plants w/wrinkled green peas(rryy)

–Offspring were round yellow,establishing the dominance of RRYY

•Resulting genotype RrYy

2) The Two factor Cross:F2

–All F1 plants were ______.He wanted to see how the alleles will segregate when F1’s are crossed w/ each other to make an F2 generation

–F2 produced 556 seeds-315 round 7 yellow and 32 were wrinkled and green

–______seeds had a combination…Therefore seed shape separated separately from color.

–This is known as ______-genes segregate independently during formation of gametes.This accounts for much of the variation in color

B.Summaryof Mendel’s Principles

•Inheritance of biological characteristics is controlled by genes from the parents

•When there are 2 or more alleles of a gene,then one is dominant and one is recessive

•Most sexually reproducing organisms have 2 adults w/ 2 copies of each gene-one from each parent.

•Alleles usually segregate independently.

C.Beyond Dominant and Recessive alleles

Exceptions to the rules

****Majority of genes have more than 2 alleles.

****Some are neither dominant nor recessive and multiple genes and alleles or genes control traits

1 ) Incomplete dominance-one allele is not completely dominant over another one

•2) ______-both alleles contribute to the phenotype—example –in chickens the allele for black feathers is codominant with white---this results in ______offspring

•3) ______-more than 2 possible alleles exist in a population(not in one organism-example-rabbits have 1 gene for coat color,but 4 possible alleles for that gene….also an example is genes for human blood type

•4)______-traits controlled by 2 or more genes’ INTERACTION-4 different genes cover ….probably control human skin color

D.Applying Mendel’s principles

–______started using fruit flies to study genetics-______They are easy to study because they produce many offspring quickly….Mendelian genetics applied to them

E. Genetics and the Environment

–Traits not determined solely by genes

•Traits determined by ______

IV.Meiosis-already covered

V.Linkage & Gene Maps

Crossing –over during meiosis separates genes on the same chromosome onto homologous chromosomes---This gives great genetic ______.