Transcript review 13-15

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Heredity-transmission of traits from 1
generation to the next
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Genetics-study of heredity & variation
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Genes-segments of DNA
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Gemetes-reproductive cells (sperm, egg)
These are haploid (n)
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Somatic cells-body cells-diploid (2n)
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Fusion of gametes = zygote
Locus-location of a gene on a
chromosome
Genome-the complete complement of
an organisms’ genes
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Karyotype-a display of all pairs of
homologous chromosomes in a cell,
arranged by size & shape
Homologous chromosomes-those that
carry the genes that control the same
traits
Autosomes- non-sex chromosomes
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Meiosis-production of gametes
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Is preceded by DNA replication
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Result is 4 haploid daughter cells
Meiosis I – homologous chromosomes
separate
 Crossing over occurs
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Crossing over
 Prophase I
 Synapsis-joining of homologous
chromosomes along their length
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This is called a tetrad
Chiasmata-place where crossing over
occurs (where homologous
chromosomes overlap)
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Meiosis II-sister chromatids separate
Synapsis & crossing over do not occur
during mitosis
Tetrads line up in metaphase I
instead of just sister chromatids
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If a heart cell of an animal has 36
chromosomes how many
chromosomes does its sperm cell
have?
Independent assortment @
Metaphase I
Alterations of generations
 Plants & some algae
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Haploid & diploid life cycle
Diploid stage- sporophyte (meiosis
makes haploid spores/that divide via
mitosis to make a gametophyte
Haploid stage- gametophyte (makes
haploid gametes via mitosis & then
fertilization occurs making diploid
zygote)
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**a multicellular haploid stage occurs
(this does not occur in animals)
Ch14
 True-breeding-plants that selfpollinate & so all offspring are of the
same type
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Hybridization- Crossing 2 truebreeding plants
The true breeding plants are the (P)
parental generation
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Their offspring are the F1 generation
If the F1 are X’ed then an F2
generation results
Alleles-diff versions of a gene
 Recessive
 Dominant-fully expressed
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Homozygous-2 of the same alleles
 Heterozygous-2 diff alleles
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Phenotype-expressed trait
 Genotype-the genetic makeup
 Testcross-X’ing recess indiv w/an
indiv showing the dom phenotype to
find out if the organism is homo, or
hetero
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Monohybrid cross-cross studying only
1 characteristic
Dihybrid-cross to study 2 char
A 3:1 ratio suggests that both parents
are heterozygous
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The phenotypic ratio of a typical F2
generation w/Mendelian inheritance is
9:3:3:1
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An organism with the genotype SsVv
can have what possible gametes?
SV
 Sv
 sV
 sv
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Codominance-2 alleles are dominant
& affect phenotype in 2 diff but =
ways (blood type)
Incomplete dominance-when the F1
hybrids have a phenotype in b/w both
parents usually a 1:2:1 ratio
Multiple alleles- many diff alleles for a
trait (Blood type)
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Pleiotropy- makes it have phenotypic
effects
epistasis- a gene at 1 locus affects a
gene at another locus
Polygenic inheritance-2 or more
genes have an additive effect on a
single character (height, skin)
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Pedigree-family tree tracking a gene
through generations
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Ch15
Chromosome theory of inheritance:
 Genes have specific locations on
chromosomes
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Sex-linked genes- genes on the sex
chromosomes (X or Y)
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Linked genes-genes on the same
chromosome that tend to be inherited
together
Recombination-the production of
offspring that have a new
combination of genes than those of
the parents
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Parental types-receive nonrecombinant genes
Recombinants-get the new
combination of genes
Genetic map-ordered list of genes &
their loci on a chromo
 Linkage map-based on recombination
freq’s
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A freq of 50% indication that the
genes are on diff chromo’s
Sex-linked traits are passed on to
sons from their mom
Fathers pass on sex-linked traits to
daughters but not sons
 Males are Hemizygous
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Cytogenetic map-A map of a chromosome
that includes the positions of genes
relative to visible chromosomal features,
such as stained bands
Barr body-inactivated X chromosome
Nondisjunction-when homologous
chromosomes do not separate in Meiosis I
or sister chromatids do not separate in
Meiosis II
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Aneuploidy-offspring w/incorrect
chormo #
Polyploidy-having more than 2
complete sets of chromo’s
Monosomic
 Trisomic
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Deletion-a piece of the chromo is lost,
so the chromo is missing genes
Duplication-the fragment that broke
off (above) attaches to its sister
chromatid
Inversion-fragment breaks off, &
reattached to original position but
inverted
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Translocation-the fragment joins a
nonhomologous chromosome
Down’s syndroms-trisomy 21
 Klinefelters syndrome-XXY
 Turners syndrome-X
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