Heredity
Transcript of Heredity
How Lifecontinues
Chapter 11
Chapter 10
Heredity
“...tendency for traits to be passed from parent to offspring.”
Traits
“...alternative forms of a character, or heritable feature.”
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Dominant Form RatioF2 Generation
Dominant: RecessiveRecessive Form
Purple flowers White fowers
Yellow seeds Green seeds
Round seeds Wrinkled seeds
Green pods Yellow pods
Axial flowers Terminal flowers
Tall plants Dwarf plants 2.84:1(3/4:1/4)
3.14:1(3/4:1/4)
2.95:1(3/4:1/4)
2.82:1(3/4:1/4)
2.96:1(3/4:1/4)
3.01:1(3/4:1/4)
3.15:1(3/4:1/4)
705:224
6,022:2,001
5,474:1,850
428:152
882:299
651:207
Inflated pods
787:277
TABLE 10.1
Character
SEVEN CHARACTERS MENDEL STUDIED IN HIS EXPERIMENTS
Constricted pods
Can we figure out if a purple-flowering plantis Pp or PP?
Testcross
Mendel’s Theory of Heredity
Parents do not transmit traits directly; they transmit trait information in the form of “factors”
Each parent has two copies of a trait factor
Alternative forms of a factor (alleles) lead to alternative traits
The two alleles an individual has do not affect each other
The presence of an allele does not guarantee that a trait will be expressed
Homozygoushave two alleles that are the same
Heterozygoushave two alleles that are different
For a certain trait, an individual can be...
Mendel’sLaw of Segregation
Two alleles of a trait separate during the formation of gametes; half the gametes carry one and half carry the other
Mendel’s Law of IndependentAssortment
Inheritance of one trait does not influence the inheritance of another trait
Many traits exhibit Mendelian inheritance
Genes
The Central Dogma
Phenotype
Genotype
Mendel’s Theory of Heredity
Parents do not transmit traits directly; they transmit trait information in the form of genes
Each parent has two copies of a trait gene
Alleles, alternative forms of a gene, lead to alternative traits
The two alleles an individual has do not affect each other
The presence of an allele does not guarantee that a trait will be expressed
Chromosomes
Section 8.3
Section 9.3
Fig. 10.6
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
p
Locus for firstgene containingallele P or p
Locus for secondgene containingallele Y or y
Paternal homologue
Homologouschromosomes
Maternal homologueY
Homozygousgenotype YY
YP
Heterozygousgenotype Pp
Two kinds:
Autosomes
Sex Chromosomes
Sickle-CellDisease
Autosomal Recessive
Huntington’s Disease
Autosomal Dominant
Mitosis
The division of cells
Co 8
Section 8.4
Section 9.4
Meiosis
The formation of gametes
Sections 9.1 - 9.4
Sections 8.1 - 8.4
Page 183
Many traits do not follow Mendelian Inheritance
Sex-Linked Traits
http://www.uic.edu/classes/bms/bms655/lesson6.html
X-Linked Dominant
X-Linked Dominant[A] mode of genetic inheritance by which a dominant gene is carried on the X chromosome. As an inheritance pattern, it is less common than the X-linked recessive type. In medicine, X-linked dominant inheritance indicates that a gene responsible for a genetic disorder is located on the X chromosome, and only one copy of the allele is sufficient to cause the disorder when inherited from a parent who has the disorder.
http://en.wikipedia.org/wiki/X-linked_dominant
http://www.uic.edu/classes/bms/bms655/lesson7.html
X-Linked Recessive
X-Linked Recessive
http://en.wikipedia.org/wiki/X-linked_recessive
[A] mode of inheritance in which a mutation in a gene on the X chromosome causes the phenotype to be expressed (1) in males… and (2) in females who are homozygous for the gene mutation...
X-linked inheritance means that the gene causing the trait or the disorder is located on the X chromosome.
X-Linked Recessive
Red-Green Color BlindnessHemophilia AHemophilia BDuchene Muscular DystrophyBecker’s Muscular Dystrophy
http://en.wikipedia.org/wiki/X-linked_recessive_inheritance
Polygenic Inheritance
“When multiple genes act together to influence a character such as height or weight...”
Continuous Variation
Pleiotropic
“Often, an individual allele has more than one effect on the phenotype.”
Sickle-Cell Disease
Cystic Fibrosis
Incomplete Dominance
“...a heterozygous phenotype that is intermediate between those of the parents.”
Epistasis
“...an interaction between the products of two genes in which one of the genes modifies the phenotypic expression produced by the other.”
Codominance
“...the effects of both alleles are expressed.”
Environmental Effects
Linkage
Homologous Recombination
Mendel’s Law of IndependentAssortment
ChromosomalDisorders
Somatic cells are diploid
Gametes are monoploid
Nondisjunction
“The failure of chromosomes to separate correctly during meiosis I or II...”
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Figure 10.24 Nondisjunction in anaphase ICopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Metaphase l
Anaphase l
Nondisjunction:homologouschromosomes failto separate
Metaphase ll
Results in four gametes: two are n+1 and two are n–1
Aneuploidy
“...an abnormal number of chromosomes.”
Down Syndrome
trisomy 21
Nondisjunctionof sex chromosomes
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X
Y
O
XX
Nondisjunction
XX
Eggs
XOXXX
Female(Turner
syndrome)
Female(triple X)
OY
NonviableMale
(Klinefeltersyndrome)
XXY
SpermXY
Male
Female