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Heredity o Heredity parent to offspring o Heredity = the passing of traits from parent to offspring
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Genetics genes oTraits are controlled by genes, so therefore, inherited o Genetics is the study of how traits are inherited
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GREGOR MENDEL father oFirst known geneticist and “father of genetics” pea oStudied pea plants
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Asexual Reproduction Reproduction involving only one parent organism; offspring are identical to parent (clone).
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Sexual Reproduction Process in which two parents contribute genes to form a new individual; offspring are more diverse
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Chromosomes An organized structure of DNA (contains genetic info) found in the nucleus
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Genes Segment of DNA, found on a chromosome, that determines the inheritance of a particular trait.
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Alleles One of a pair of genes that determine a specific trait
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DOMINANT mask oA Dominant trait will always be expressed and will “mask” or hide a recessive trait oExample: Hh (shows dominant trait even though it contains a recessive allele)
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RECESSIVE dominantA recessive trait can only be expressed if there are no dominant alleles present Example: hh (2 recessive alleles)
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oExample dominant brown hides oExample: Eye color—Brown color is dominant and blue is recessive. A person can have a brown allele and a blue allele but still have brown eyes because the brown allele is dominant and “hides” the blue allele.
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Rr Example: R= dominant r = recessive capital lower caseGenerally, dominant alleles are represented with a capital letter, and recessive alleles are represented with a lower case letter.
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Homozygous An organism that has two identical alleles for a trait Example: HH or hh
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same homozygousFor example: BB or bb. o“Purebred” species have two alleles of the same trait, and therefore would be represented by two of the same letters. This is also called homozygous. For example: BB or bb. Purebred
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Heterozygous lettersAn organism that has two different alleles for a trait represented by two different “letters” For instance: Bb
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genotypeBB, Bb, or bb. oThe alleles present in the organism are referred to as its genotype. For instance, BB, Bb, or bb. Genotype
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PHYSICAL PHENOTYPE oThe PHYSICAL trait that shows, regardless of genotype is called a PHENOTYPE. BlueBrown oFor instance, Blue or Brown Eyes. Phenotype
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oThree or more alleles for a particular gene. Multiple Alleles
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oTwo different alleles (both dominant) oBoth alleles are present in the phenotype. Co-Dominance
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oTwo different alleles (both recessive or not dominant over the other) oNeither allele is present in the phenotype, creating a new trait. oExample – Red flower bred with a white flower creating a pink flower Incomplete Dominance
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Complete Dominance, Co- Dominant and Incomplete Dominance Complete Dominance Co-DominantIncomplete Dominance Alleles RRRed RrRedRed/WhitePink rrWhite R-Red r- White
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Using a Punnett Square… oUsed to help predict Mendelian genetics
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Steps for using the Punnett square: (genotype) 1)One parent’s alleles (genotype) go along the top 2)The other parent’s alleles go down the side. 3)You fill in the squares like doing the communicative property of multiplication. 4)See Below:
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Steps for using the Punnett square: Let’s say the parents are Bb and Bb (the same genotype for eye color). What would be their phenotype? Brown Eyes BbBb B b So you would predict: 1/4 1/4 offspring to be BB, or Brown Eyes 1/2 Brown 2/4 or 1/2 to be Bb, or Brown Eyes 1/4Blue and 1/4 to be bb or Blue eyes BB bbBb
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Using a Punnett Square Clip
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Heredity Heredity by Brainpop 1What do we call different forms a gene may have for a trait? 2What height of pea plant (tall or short) did Mendel find to be dominant? 3Which kind of trait can’t be passed from parent to child? a)Eye colorb) heightc) broken arm
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Let’s try some practice problems…
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Practice Problem #1 Predict the fur color of the offspring of a brown heterozygous hamsters and a white homozygous hamster. Brown is dominant. White is recessive. Use any letter you like.
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Practice Problem #1 Bbbb Bbbb B b bbbb
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Practice Problem #2 Predict the offspring of 2 white homozygous cows. Black is dominant over white. Use any letter you like.
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Practice Problem #2 bb bbbb
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Practice Problem #3 Predict the offspring of 2 Grey Heterozygous rats. Gray is dominant over white, which is recessive. Use any letter you like.
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Practice Problem #3 GGGg gg G g GgGg
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Practice Problem #4 Predict the pea shape of the offspring of one Heterozygous Round Pea plant and one homozygous wrinkled pea plant. Round is dominant over wrinkled. Use any letter you like.
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Practice Problem #4 Rrrr Rrrr R r rrrr
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Practice Problem #5 you don’t have to write this one down… What are the chances of having a boy or a girl? How would you solve this one?
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Practice Problem #5 XXXY XXXY XXXX
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