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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)
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:
•A brown tall rabbit is mated with a white short rabbit. Brown and tall are dominant. Construct a punnett square
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
•Pleiotrophic- when genes affect more than one phenotypic characteristic
•Polygenic inheritance- additive effects of two or more genes on a single phenotypic character.
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+
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
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