7th Grade Chapter 5 Notes

7th Grade Chapter 5 Notes

by Mac McDowell

Open Ended

This albino deer had a mother with a normal coat.  Why do you think it looks so different?

Mendel and H​is Peas

​Lesson 1

​Mendel's Experimental Methods

​1. During the 1850s Gregor Mendel studied genetics by doing controlled experiments with pea plants.

​2. peas were used because they reproduced quickly, easily observed traits and the ability to control which plants reproduced

​3. pollination is when pollen lands on the pistil of a flower

​4. this allows sperm from the pollen to fertilize the egg in the pistil.

​

​cont

• ​peas con pollinate two ways

• ​self pollination is when pollen from one plant, lands on the pistil of the same plant

• ​cross-pollinations is when pollen from one plant, reaches the pistil of another.

Multiple Choice

Pea plants can pollinate ___________ ways

• one

• two

• three

• four

Multiple Choice

_____________ occurs when pollen lands on the pistil of a flower.

• fertilization

• pollination

• reproduction

Multiple Choice

_______________________ is when pollen from one plant, lands on the pistil of another.

• self pollination

• cross pollination

• fertilization

​true breeding plants

​1. Mendel began his experiments with true breeding plants

​2. when a true breeding plant self pollinates, it always produces offspring with traits that match the parent.

​ex. a true breeding plant with wrinkles seeds self pollinates and produces only wrinkled seeds

​Mendel's Cross Pollination

• ​by controlling which plants pollinated other plants, Mendel knew which traits the parents had.

• ​The picture shows this happening between a plant with white flowers and one with purple flowers

Multiple Choice

A plant, that when self pollinated, only produces plants with the same traits as the parent.

• pollination

• hybrid

• cross breeding

• true breeding

Multiple Choice

How did mendel control which plants pollinated other plants?

• by removing the stamens from one plant and pollinating them with pollen from a different plant

• by leaving the plants to grow in the garden naturally

​Mendel's Results

​1. When he had enough true breeding plants, he cross-pollinated selected plants.

​2. a cross between true breeding purple plants only produced purple and between white, only produced white

​3. when true breeding purple plants crossed with white, the offspring had all purple flowers

Multiple Choice

What are the results after Mendel crossed the parent generation of a true breeding white flower, with a true breeding purple flower, to create the first generation?

• some purple flowers, some white

• all purple flowers

• all white flowers

Open Ended

What is a question Mendel might have asked himself with his results from the first generation?

​Second Generation

​1. the first generation is called hybrid plants

​2. this means they came from true breeding plants with different forms of the same trait.

​3. Mendel took these hybrids and cross pollinated them

​cont.

• ​some off these offspring had white flowers, even though all parents had purple flowers

• ​the trait that disappeared in the first generation, reappeared in the second

• ​this happened with other plea plant traits too

Multiple Choice

What do we call a cross between two plants with different forms of the same trait?

• fertilization

• pollination

• hybrid

Multiple Choice

What plants did Mendel use to create the second generation?

• different plants

• the same original parents

• the plants produced from the first cross

Multiple Choice

What were the results of the second generation?

• 100% purple flowers

• 25% purple flowers 75% white flowers

• 100% white flowers

• 75% purple flowers 25% white flowers

​more hybrid crosses

• ​Mendel repeated these steps crossing plants with different traits shown to the right

• ​he found that the first generation, a trait was always hidden, but reappeared the next generation

• ​The ratio between them was 3:1

​Mendel's conclusions

​1. he concluded that two genetic factors control each inherited trait

​2. when organisms reproduce, each reproductive cell, contributes one factor for each trait.

​3. he hypothesized that hybrids have one factor for purple and one for white, but only showed the purple

​4. this explains how white reappears in the next generation

​cont.

​5. he hypothesized purple is the only one seen because it blocks the white

​6. a genetic factor that blocks another is called a dominant trait

​7. a genetic factor that is blocked by the presence fo a dominant factor is called a recessive trait

​8. a recessive trait is only observed when two recessive genetic factors are present

Multiple Choice

A genetic factor that blocks another genetic factor

• dominant trait

• recessive trait

• hybrid

• mitosis

Multiple Choice

A genetic factor that is blocked by the presence of a dominant factor

• dominant trait

• recessive trait

• hybrid

• offspring

​Understanding Inheritance

Lesson 2​

​What controls traits?

​1. Mendel concluded that two factors- one from each parent - control each trait.

​2. chromosomes contain genetic information that controls traits

​3. Mendel's factors are part of chromosomes, chromosomes are inherited, one from each parent

Multiple Choice

How many chromosomes are inherited from each parent?

• 1

• 2

• 3

• 4

Multiple Choice

In Mendel's peas, how many factors control a trait?

• 1

• 2

• 3

• 4

Multiple Choice

Where are the factors that control traits located?

• brain

• chromosomes

• mitochondria

• hybrid

​Genes and alleles

​1. each chromosome can have information about hundreds or even thousands of traits.

​2. a gene is a section on a chromosome that has genetic information for one trait.

​3. offspring inherit two genes for each trait, one from each parent.

​4. The different forms of a gene are called alleles.

Multiple Choice

For the traits that Mendel studied, the offspring peas inherited one factor that control's a trait from each parent, as there is one factor per chromosome, one chromosome from each parent, and those chromosomes combine during fertilization to form the offspring pea.

• true

• false

Multiple Choice

The different forms of a trait are called

• meiosis

• hybrid

• peas

• alleles

​Genotype and Phenotype

​1. For flower color, they could have two alleles for purple, two for white, or one for white, one for purple.

​2. How a trait appears or is expressed is the trait's PHenotype or PHysical characteristic.

​3. the two alleles that control the phenotype of a trait are called the trait's genotype.

​4. the genotype is what the two alleles are

Multiple Choice

the two alleles on the chromosomes are called its

• phenotype

• genotype

• allele

• hybrid

Multiple Choice

How a trait appears, how it is expressed, or its PHysical characteristic 

• phenotype

• genotype

• allele

• zygote

​Symbols for genotypes

​1. scientists use symbols to represent the alleles in a genotype

​2. Uppercase letters represent dominant alleles

​3. lowercase letters represent recessive alleles

​4. The dominant allele is written first, if present

Multiple Choice

uppercase letters represent _________________ alleles

• dominant

• recessive

Multiple Choice

lowercase letters represent __________________ alleles

• dominant

• recessive

​round vs. wrinkled

• ​a round seed can have two genotypes RR or Rr

• ​A Rr still produces a round seed because it is the dominant trait

• ​a wrinkled seed has the recessive genotype rr

Homozygous and Heterozygous

​1. When the two alleles of a gene are the same, its genotype is homozygous, both RR and rr are homozygous

​2. if two alleles of a gene are different, its genotype is heterozygous, Rr

Multiple Choice

If two alleles for a gene are the same we call it

• homozygous

• heterozygous

• hybrid

• clone

Multiple Choice

If two alleles for a gene are different, we call it

• homozygous

• heterozygous

• inferior

• inheretance

​Modeling Inheritance

​1. Flipping a coin that has two sides gives you a 50% chance of heads and 50% chance of tails or a 1:1 ratio

​2. Plant and animal breeders use a method for predicting how often a trait will appear in offspring

​3. A punnett square is a model used to predict possible genotypes and phenotypes of offspring.

​

​Punnett Squares

• ​A cross between two plants that are heterozygous for height shows off spring can be TT,Tt, or tt

• ​the ratio of genotypes is 1:2:1

• ​The ratio of phenotypes is 3 tall:1 short

• ​

​Using ratios to predict

​1. you cannot expect 4 of these offspring to always have a 3:1 ratio, but the larger the group, the overall ratio will be more predictable

​

​2. A pedigree is another model that can show inherited traits.

​Pedigrees

• ​a pedigree shows phenotypes of genetically related family members

• ​it can also determine genotypes

• ​If the parents don't show a trait, but have offspring that do, it is a recessive trait

​incomplete dominance

• ​when the offspring's phenotypes is a combination of the parents' phenotypes

• ​ex. a white and red flower producing a pink flower

​Codominance

• ​when both alleles can be observed in a phenotype

• ​ex a red coat and white coat producing a roan pattern

Multiple Choice

when the offspring's phenotype is a combination of the parents' phenotypes, ex a red and white flower, producing a pink flower

• incomplete dominance

• complete dominance

• inheritance

• hybrid

Multiple Choice

when both alleles can be observed in a phenotype, ex a red cow and a white cow producing a roan coat color

• incomplete dominance

• codominance

• inheretance

• hybrid

​multiple alleles

• ​unlike pea plant traits, some genes have more than two alleles, like human ABO blood type (I^a I^b and i)

• ​results in four blood types, A, B, AB, or O

• ​A and B are codominant, but dominant to the O

​Polygenic Inheritance

• ​occurs when multiple genes determine the phenotype of a trait

• ​many possible phenotypes

• ​ex eye and skin color

Multiple Choice

genes that have more than two alleles inheritance patterns

• multiple alleles

• polygenic inheritance

• codominance

• incomplete dominance

Multiple Choice

occurs when multiple genes determine the phenotype of a trait

• multiple alleles

• polygenic inheritance

• codominance

• incomplete dominance

​Genes and the environment

​1. genotype determines phenotype

​2. environment can also affect phenotype

​3. ex. hydrangeas can be different colored flowers depending on how acidic the soil is.

​4. your health decisions can have an impact on what diseases you are likely to get due to genetics actually occur