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What is the study of heredity called?
What is the study of heredity called?
Genetics
Gregor Mendel developed the basic principals of heredity with knowledge of genes and chromosomes.
Gregor Mendel developed the basic principals of heredity with knowledge of genes and chromosomes.
False
Which of the following characteristics did Mendel choose to study in pea plants?
Which of the following characteristics did Mendel choose to study in pea plants?
What are two contrasting characteristics of pea plant seeds?
What are two contrasting characteristics of pea plant seeds?
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In Mendel's experiments, what was the ratio of dominant traits to recessive traits in the F2 generation?
In Mendel's experiments, what was the ratio of dominant traits to recessive traits in the F2 generation?
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What is the name of the principle where one form of a hereditary trait dominates or prevents the expression of the recessive trait?
What is the name of the principle where one form of a hereditary trait dominates or prevents the expression of the recessive trait?
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What is the name of the principle where chromosomes are combined from both the sperm and egg?
What is the name of the principle where chromosomes are combined from both the sperm and egg?
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What is the name of the process where alleles are separated so that each gamete has only one allele for each trait?
What is the name of the process where alleles are separated so that each gamete has only one allele for each trait?
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What is the term to describe the genetic makeup of an individual?
What is the term to describe the genetic makeup of an individual?
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What is the term to describe the physical appearance of an individual?
What is the term to describe the physical appearance of an individual?
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What is the name of the cross where an organism with a dominant phenotype is crossed with a homozygous recessive individual?
What is the name of the cross where an organism with a dominant phenotype is crossed with a homozygous recessive individual?
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What is the name of the condition where both alleles are dominant and both are expressed in the heterozygote?
What is the name of the condition where both alleles are dominant and both are expressed in the heterozygote?
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What is the name of the condition where the dominant allele is only partially expressed in the heterozygote, leading to a phenotype that is a blend of the two homozygous forms?
What is the name of the condition where the dominant allele is only partially expressed in the heterozygote, leading to a phenotype that is a blend of the two homozygous forms?
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If two genes are located on the same chromosome, they are said to be linked.
If two genes are located on the same chromosome, they are said to be linked.
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What is the name of the process where chromosomes exchange segments during meiosis?
What is the name of the process where chromosomes exchange segments during meiosis?
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Human blood types have 3 alleles for blood type.
Human blood types have 3 alleles for blood type.
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Females have two X chromosomes and males have two Y chromosomes.
Females have two X chromosomes and males have two Y chromosomes.
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Study Notes
Gregor Mendel and Mendelian Genetics
- Gregor Mendel (1823-1884) studied heredity.
- Mendelian genetics is the study of heredity.
- Mendel worked with pea plants.
- Pea plants are inexpensive, easy to control reproduction, and produce many offspring with contrasting characteristics.
- Contrasting characteristics include: seeds (round or wrinkled), seed color (yellow or green), height (tall or short), flowers (white or purple), and pod color (yellow or green).
Mendelian Genetics: F2 Generation Results
- Mendel's experiments involved cross-pollination of pure plants with contrasting characteristics.
- Examples include:
- Purple flowers x White flowers
- Yellow seeds x Green seeds
- Round seeds x Wrinkled seeds
- The F2 generation (the second filial generation) exhibited traits in a specific ratio, like 3.15:1 for purple to white flowers, and 3.01:1 for yellow to green seeds.
Mendel's Principles of Heredity
- Dominance: One form of a hereditary trait dominates the other.
- Segregation: Segregation of chromosomes during meiosis.
- Recombination: Combining of chromosomes from sperm and egg (fertilization).
- Independent Assortment: Independent segregation of genes forming gametes.
Pea Plant Characteristics
- Peas reproduce sexually.
- Each trait is influenced by two alleles (one from each parent).
- Alleles are represented by letters.
Mendel's Work: The Next Generation
- Mendel cross-pollinated pure plants. For example, he crossed "pure tall" with "pure short".
- The F1 generation (first filial generation) showed only one trait. The offspring were all tall.
- Mendel then used two F1 tall plants and crossed them, creating the F2 generation.
- The F2 generation showed both tall and short traits in a 3:1 ratio.
Punnett Square
- A tool used to predict the outcome of genetic crosses.
- Each box represents a possible offspring.
- Mendel used Punnet Squares accurately predict the outcomes of crosses he didn't even perform.
Hybrid Cross
- A cross between two heterozygotes.
- There are three possible genotypes in a 1:2:1 ratio.
- The phenotypic ratio is 3:1 (3 dominant:1 recessive).
Test Cross
- Determining the genotype of an organism displaying a dominant phenotype by crossing it with a recessive individual.
- If any recessive offspring result, the original individual is heterozygous (hybrid).
- Example: a brown-eyed individual testing for BB vs Bb
Codominance
- Some traits are controlled by two different dominant alleles. Both alleles are expressed.
- Heterozygotes exhibit both phenotypes simultaneously.
- Example: coat color in cattle (Roan).
Incomplete Dominance
- An allele is only partially dominant over another.
- In heterozygotes, the phenotype is a blend of the two homozygous forms.
- Example: Snapdragons (flower color).
Mendel's Law of Independent Assortment
- Two traits are inherited independently if the genes are on different chromosomes.
- During gamete formation, alleles for different traits segregate independently of each other.
Gene Linkage
- If genes for different traits are on the same chromosome, they are linked (inherited together).
- Examples include eye and hair color.
- Crossing over in meiosis can cause recombination of linked genes, increasing variability in the offspring.
Multiple Alleles
- Some traits are controlled by more than two different alleles.
- Example: human blood types (controlled by three alleles: IA, IB, and i).
Sex Determination
- Males and females differ in one pair of chromosomes (sex chromosomes). Humans have 23 pairs of chromosomes in total. XX determines a female and XY determines a male. The man determines the sex of the child.
- In humans, the sex chromosomes are "X" and "Y".
- Genes on the X chromosome are called sex-linked. Often recessive genes on the X chromosome are expressed more often in males because males have only one X chromosome.
Sex Linkage
- Some genes are located on the X chromosome.
- Recessive sex-linked genes are more commonly expressed in males because they only have one copy of the X chromosome.
- Examples include hemophilia and colorblindness. These traits are more frequently observed in males because females need to inherit two recessive alleles.
Pedigree Charts
- Illustrate the inheritance of traits in families.
- A tool used to track the inheritance of genetic traits across multiple generations.
- Example: pedigree illustrating albinism.
Heredity and the Environment
- Environment interacts with genes affecting the expression of inherited traits. Example: effect of light on chlorophyll production in plants. Example: Effect of temperature on the coat color of Himalayan rabbits.
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