genes and inheritance
DESCRIPTION
Chromosome. Trait. Protein. Gene. Genes and Inheritance. Genes contain the information for the production of proteins, which specify traits. Since genes are inherited, traits are also inherited. Location of Genes. Chromosome from egg (mom). Chromosome from sperm (dad). - PowerPoint PPT PresentationTRANSCRIPT
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Trait
Gene
Protein
Genes and Inheritance
Genes contain the information for the production of proteins, which specify traits.
Since genes are inherited, traits are also inherited.
Chromosome
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Location of Genes
In sexually reproducing organisms, cells have a homologous pair of chromosomes (one from each parent).
Chromosomes from a homologous pair have the same genes but can have different alleles.
Allele: different form of a gene
May be dominant or recessive.
Chromosome from sperm(dad)
Chromosome from egg
(mom)
Homologous pair of chromosomes
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Gregor Mendel: Father of Genetics
Genetics: branch of biology dealing with heredity
Gregor Mendel (1822-1884)was an Austrian monk who is regarded as the father of genetics.
Mendel used pea plants to study the inheritance patterns of many traits.
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Mendel’s View of Inheritance
Parent A Parent B
Offspring
New Idea (Mendel)
Inherited traits behave as discrete units
Parent A Parent B
Offspring
Old IdeaBlending of
parental traits
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Mendel’s Pea ExperimentsMendel examined a small number of phenotypic characters or traits in peas.
Dominant alleles masked recessive alleles.
Seed shape
round dominant over wrinkled
Seed color
yellow dominant over green
Pod shape
inflated dominant over constricted
Pod color
green dominant over yellow
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Using a Punnett Square: Monohybrid Crosses
Calculates outcomes of genetic crosses.
Important vocabulary:
Homozygous dominant
Heterozygous
Homozygous recessive
Each parent provides
two gametes for the grid
Gametes
P
p
GametesP p
Parents
Pp Pp
X
Offspring
pp
PP Pp
Pp
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Genotype and Phenotype
The genotype of an organism refers to its genetic make-up.
The phenotype of an organism refers to its observable features or traits.
pp(homozygous)
White
PP(homozygous)
Purple
Pp(heterozygous)
Purple
Pp(heterozygous)
Purple
Genotype Phenotype
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Results of Mendel’s Experiments
Seed shape
Round Wrinkled
5474
1850
7324
RoundWrinkledTOTAL
2.96 : 1
Seed color
Yellow Green
6022
2001
8023
YellowGreenTOTAL
3.01 : 1
Pod color
Green Yellow
428
152
580
GreenYellowTOTAL
2.82 : 1
Flower position
Axial Terminal
651
207
858
AxialTerminalTOTAL
3.14 : 1
Pod shape
Inflated Constricted
882
299
1181
InflatedConstrictedTOTAL
2.95 : 1
Stem length
Tall Dwarf
787
277
1064
TallDwarfTOTAL
2.84 : 1
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Mendel’s Law of Segregation
Each pair of alleles is separated into different gametes and into different offspring.
Gametes contain only one copy of a gene since they only receive one chromosome from each homologous pair.
Gametes (sperm Or egg cells)
Homologous pair of chromosomes, each has a copy of the gene on it (A or a)
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aBaB
Gametes
AbAb
Intermediate Cells
Law of Independent Assortment
Alleles for different traits are sorted independently of each other.
All combinations of alleles are distributed to gametes with equal probability.
Genotype: AaBb
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Polydactylism is a
dominant trait
Selected Hereditary TraitsDominant Recessive
Right handedness Left handedness
Hitch-hiker’s thumb Normal thumb
Polydactylism (extra digits) Normal digits
Pattern baldness Normal hair
Free ear lobes Attached ear lobes
Hitch-hiker’s thumbAttached ear lobe
Handedness
Free ear lobe
In this crowd of men, almost all
show some degree of pattern
baldness, a dominant trait.
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Dominant
Human Tongue Roll
The ability to roll the tongue into a U-shape when viewed from the front is controlled by a dominant allele.
Recessive
Phenotype: Cannot roll tongue
Allele: t
Phenotype: Can roll tongue
Allele: T
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Punnett Square Practice
1. Brown hair (B) is dominant over lighter hair
colors (b). If two heterozygotes for this trait
mate, what are the:
a. genotype frequencies
b. phenotype frequencies
of the offspring?
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Punnett Square Practice
2. Dwarfism (D) is dominant over normal height (d).
If a person of normal height and a dwarf who is
homozygous dominant mate, what are the
chances of having a child that is also a dwarf?
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Punnett Square Practice
3. Polydactyly, or having extra digits (P) is dominant over
having five digits on each limb (p). If a woman with
polydactyly mates with a normal male, then:
a. What are the possible genotypes of the woman?
b. What is the genotype of the male?
c. Create two Punnett Squares displaying their
possible children.
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Punnett Square Practice
4. Tallness in pea plants (T) is dominant to
shortness (t). Round seeds (R) are dominant to
wrinkled seeds (r). Set up a Punnett Square
showing the mating results of two plants that are
heterozygous for both traits.