Genetics

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Genetics

• The Study of Inherited Characteristics
• Ch 10.1 and Ch12

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Meiosis in the Gonadsmakes gametes
Sperm
Meiotic cell division
Egg
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Chromosome

DNA Code for traits
X
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Gene
Hair Color

• Segments of DNA
• Code for a trait

X
Eye Color
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Gene Segment For Hair color

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Trait

• Characteristic
• Feature
• Variations in a population

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Dominant Trait

• Dominates
• Shows in the outward appearance
• Even when recessive trait is present
• Bb

BB or Bb
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Recessive Trait
Albinism

• hidden
• May be masked by a dominant trait
• Bb

bb
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Alleles

• Letters of the alphabet
• Code for a trait
• One from father
• One from mother

RR Rr TT Tt
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• Recessive Allele
• Lower case letter of the alphabet
• Codes for recessive traits

• Dominant Allele
• Upper case letter of the alphabet
• Codes for dominant traits

R
r
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Chromosomes in Nucleus
Gene Segments For a Trait A or a
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Monohybrid Cross

• Cross for one trait
• Example
• Hair color

• B b
• B BB Bb
• B BB Bb

Punnet Square
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F1 Generation

• Genetic Cross
• Mating
• F1
• Children
• 1st filial generation

Parents B b
B BB Bb
B BB Bb
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2nd Filial Generation- F2

• F1
• F2

B B
b Bb Bb
b Bb Bb

• Children of the cross between the children of an
  F1
• Incest among F1
• Only after pure x pure

B b
B BB Bb
b Bb bb
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Phenotype

• Outward appearance
• Trait that is shown
• Bb looks brown (has b white allele)

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Genotype

• Bb

• Allele set
• True genetic makeup of the chromosome

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• Homozygous
• Pure condition
• 2 same case alleles
• BB dominant
• bb recessive

• Heterozygous
• Hybrid condition
• 2 different case alleles
• Bb appears dominant

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Mendelian Genetics Review

• See Encarta CD-ROM

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Dihybrid Cross

• Cross with
• two traits
• Example
• Hair Color
• Eye Color
• 2 types of
• alleles

parents
Children Children Children Children
Children Children Children Children
Children Children Children Children
Children Children Children Children
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Codominance

• Incomplete dominance
• Hybrid is a blend of traits
• Example
• RRred
• Rrpink
• rrwhite

Pink Carnation
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Multiple Alleles

• More than one type of allele for a trait
• Example
• Blood Type

• TYPES
• A IAIA, IAi
• B IBIB , IBi
• AB IAIB
• O ii

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X-Linked Traits

• Female
• XX
• Add eye trait
• XRXR or XRXr
• XrXr
• Male
• XY
• Add eye trait
• XRY or XrY
• Y is empty

• Sex-linked
• Trait in on the sex chromosome
• XX
• Female
• XY
• Male
• ExRed white eyes

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Karyotype
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Chromosome Number
Homologous Chromosomes are the sets of each pair

• Different for different species
• Full set 2NDiploid
• N
• pairs
• 1 pair from mother
• 1 pair from father
• Humans 23 pairs or
• 46 total

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Autosomes Sex Chromosomes
Autosomes 1-22 for all traits except sex
Sex chromosomes Pair 23 XX(female)
or XY(male)
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Down Syndrome 3 of 21
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Klinefelters XXY
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Pedigree Charts

• Male
• Female
• Sexual Union
• Offspring

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Pedigree Chart -Cystic Fibrosis
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Mutation
A to A G C
A T GC

• Change in DNA code
• Caused by
• Chemical damage
• Errors in Replication
• X-ray damage
• UV damage

• X

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Mutation

• Changes in the DNA code
• Changes in the final proteins made
• Changes in the organism