Heredity. By: Amber Tharpe. Genetics. The study of the passing of traits to offspring Genome All an organism’s genetic material Gene Segment of DNA that codes for a specific trait Traits Characteristics that can be inherited Ex: eye color, hair color, height.
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Heredity By: Amber Tharpe
Genetics • The study of the passing of traits to offspring • Genome • All an organism’s genetic material • Gene • Segment of DNA that codes for a specific trait • Traits • Characteristics that can be inherited • Ex: eye color, hair color, height
Genetics • Allele • variety of forms of a gene for a trait • ex: The gene for the color of pea plants has 2 different alleles→ G (green) and g (yellow)
Genetics • Genotype • Letters that represent an individual’s genetic makeup • Gg • Phenotype • Physical characteristic that corresponds to a genotype • Pea plants have a green color
Genetics • Dominant • trait that masks another • capital letter • ex: G • Recessive • trait that is masked by another • lower case letter • ex: g
Genetics • Homozygous-purebred • has 2 of the same alleles • ex: GG or gg • Heterozygous- hybrid • has 2 different alleles • ex: Gg
PunnettSquares • 2 parents heterozygous for brown eyes have children • What is the probability that their children will have blue eyes?
Dominant traits mask reccessive traits ¾ or 75% of the offspring will have brown eyes ¼ or 25% of the offspring will have blue eyes Punnett Squares
Gregor Mendel • Austrian monk • Father of Genetics • Crossed a homozygous recessive and homozygous dominant • This gave a heterozygous all with the dominant trait • Self-pollinated the heterozygous generation which gave a generation with a 3:1 ratio • The recessive trait reappeared
Mendel • Law of segregation • Alleles separate when gametes are formed
Law of Independent Assortment • Different traits are inherited separately • In metaphase I of meiosis, homologous pairs of chromosomes line up in the center of the cell randomly • Different pairs of alleles separate independently of each other when gametes are formed
Genetic Recombination • All the ways chromosomes can be mixed up during sexual reproduction to allow every individual to be different • Crossing over • Segregation of homologous chromosomes • Independent assortment
Crossing Over • Exchange of segments between homologous chromosomes • Occurs during Prophase I of meiosis • Increases genetic diversity
Carrier • Heterozygous for a recessive disease • Does not have symptoms of disease, but can pass the disease-causing allele to offspring • Ex: sickle cell anemia
Sex-linked genes • Located on X and Y chromosomes • XX- female, XY- male • Males have only one X chromosome and one Y chromosome, so they express all alleles on both chromosomes (even recessive ones) • Expressed more often in males • Ex: hemophilia A
Incomplete Dominance • Heterozygous phenotype is somewhere between the 2 homozygous phenotypes • No dominant or recessive • Ex: 4 o’clock plants- flowers can be red, white, or pink • Pink is a combination of the red and white alleles
Codominance • Heterozygous phenotype is a combination of both homozygous phenotypes • No recessive • Ex: Plants with both red and white flowers on the same plant
Multiple Allele Traits • A gene has more than 2 alleles • Ex: ABO blood types
Polygenic Traits • Traits produced by 2 or more genes • Ex: eye color, fur color
Pedigree • Family tree that shows the heredity of a trait • symbolize males • symbolize females • Shaded symbolizes having the trait • ½ shaded symbolizes being heterozygous
Karyotype • Picture of all chromosomes in a cell • Can detect some genetic diseases • Such as trisomy 21- Down Syndrome