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Chapter 13-15

Next test December 6

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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-

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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