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Chapter 13-15

Next test December 6

Study guide Corrections too

Chapter 13- Meiosis•Heredity- or inheritance transmission of

traits from one generation to the next

•Genes- coded information with traits, segments of DNA

•Gametes- reproductive cells (sperm and egg)

•Somatic cells- cells other than reproductive cells

•Locus- a specific location on a chromosome

•Asexual reproduction vs Sexual reproduction

•Life cycle- generation to generation sequence of stages in reproductive history

Chromosomes•46 human chromosomes (somatic) 2n (2

sets)•Karyotype•Autosomes vs sex chromosomes•Haploid (n) – cells with a single

chromosome set

•Fertilization- union of gametes (sperm and egg) zygote is formed

•Zygote- fertilized egg, diploid because it contains 2 haploid sets from each parent

•Meiosis- process to form gametes, reducing chromosome number by half

Meiosis •Interphase•Meiosis I

▫Separates homologous chromosomes•Meiosis II

▫Separates sister chromatids

Meiosis I•Prophase I

▫Crossing over occurs•Metaphase I

▫Homologous chromosome PAIRS line up at middle

•Anaphase I▫Duplicated homologous chromosomes

separate•Telophase I, Cytokinesis

▫2 cells result

Meiosis II•Prophase II•Metaphase II

▫Homologous chromosomes (sister chromatids) line up at center

•Anaphase II▫Sister chromatids separate

•Telophase II, Cytokinesis

Mendel and Gene Idea Chapter 14•Blending hypothesis- genetic material

mixes in a manner which blends traits

•Mendel- peas

•Traits- characteristic inherited •True-breeding – plants self-pollinate to

have same traits as parents •Hybridize- cross (or cross-pollinate)

•P generation – parent

•F1 = Offspring of P

•F2 = offspring of F1

•Genotype –

•Phenotype –

•Alleles- alternative forms of traits

•Dominant-

•Recessive-

AP Biology

Mendel’s laws•Law of segregation-

▫2 alleles for a heritable character separate during gamete production (end up in different gametes)

•Law of independent assortment- ▫Each pair of alleles segregates

independently during gamete formation.

Problem:•Homozygous black rabbit mates with a

homozygous white rabbit

Phenotypic ratio:

Genotypic ratio:

Problem:•Carry out a cross for the F1 generation:

Phenotypic ratio:

Genotypic ratio:

Problem:•A brown tall rabbit is mated with a white

short rabbit. Brown and tall are dominant. Construct a punnett square

Problem:•Use F1 to determine the F2 generation

Laws of probability govern Mendelian inheritance

•Probability of tossing heads with normal coin:

•Probability of rolling a 3 with a 6 sided die:

Law of multiplication•Used to determine probability of two or

more independent events.

•Probability that 2 girls are born in a row to a family:

•Probability that 6 girls are born in a row to a family:

Law of addition:•The probability of an event that can occur

in two or more mutually exclusive ways

•The probability of producing an F2 heterozygote:

Mendel genetics = simple genetics•Incomplete dominance – intermediate

offspring

•Codominance – both traits are shown

•Many genes exist in populations in more than two allelic forms:

•ABO blood groups:

•IA, IB, i

•Pleiotrophic- when genes affect more than one phenotypic characteristic

•Polygenic inheritance- additive effects of two or more genes on a single phenotypic character.

Pedigrees

AP BIO•Finish Chapter 15

•Lab Tuesday

•Test Thursday

AP Biology•Thomas Morgan

▫Worked with Drosophila (fruit flies)▫Discovered wild type – characteristic found

in nature▫Mutants were alternatives to the wild type

Fruit flies- carry eye color on X chromosomeWhite eyes – wRed eyes – w+

Not All organisms are XX and XY

SRY gene on Y•SRY (sex-determining region of Y) gene

was discovered in 1990.•Individuals with the SRY gene embryonic

gonads develop into testes•Individuals without the SRY gene develop

ovaries

Genes located on Sex Chromosomes•Sex-linked genes•On Y = Y-linked genes•On X = X-linked genes

▫Color blindness▫Hemophilia▫Duchenne muscular dystrophy

Problem:•Mother heterozygous for color blindness•Father is not colorblind

Results:

Barr body•Females inherit 2 X chromosomes, only 1

X chromosome is active.

•Barr body- during development 1 X chromosome per cell condenses into a compact Barr body.

•Barr bodies are not expressed.

Linked genes•Linked genes – genes located near each

other on the same chromosome and tend to be inherited together.

Crossing over•Accounts for recombination of linked

genes•Occurs in prophase I meiosis I•New combinations result in varied

offspring

Alterations of chromosome number•Nondisjunction –

▫members of a pair of homologous chromosomes do not separate properly during meiosis I

▫Or sister chromatids fail to separate during meiosis II.

▫Trisomic, monosomic cells

▫Polyploid – organisms with more than two complete sets of chromosomes

Breakage of chromosome structure•Deletion – when a chromosomal fragment

is lost•Duplication- occurs when a fragent

becomes attached as an extra segment to a sister chromatid.

•Inversion – When chromosome fragment reattaches to the original chromosome in the reverse direction

•Translocation- fragment joins a non homologous chromosome