ملخص درس Inheritance في العلوم باللغة الإنجليزية للصف السادس - الفصل الثالث (2)

Reproduction of Organisms، Module Vocabulary

Term phenotype heredity genetics dominant recessive

gene، allele genotype، homozygous heterozygous pedigree، regeneration، vegetative reproduction، asexual reproduction، budding، sexual reproduction، behavior، pollination، phototropism thigmotropism gravitropism، Definition

how a trait appears or is expressed.

the passing of traits from parents to offspring.

the study of how traits are passed from parents to offspring.

a genetic factor that blocks another genetic factor.

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

a section of DNA on a chromosome that has genetic information for one trait.

a different form of a gene.

the alleles of all the genes on an organism’s chromosomes; controls an organism's phenotype.

a genotype in which the two alleles of a gene are the same.

a genotype in which the two alleles of a gene are different.

a model that shows genetic traits that were inherited by members of a family.

a type of asexual reproduction that occurs when an offspring grows from a piece of its parent.

a form of asexual reproduction in which offspring grow from a part of a parent plant.

a type of reproduction in which only one parent organism or part of that organism produces a new organism.

a form of asexual reproduction where an organism grows on the body of its parent.

type of reproduction where the genetic material from two different cells combine, producing an offspring.

the way an organism reacts to other organisms or to its environment.

the process that occurs when pollen grains land on a female reproductive structure of a plant that is the same species as the pollen grains.

the growth of a plant toward or away from light.

the response of a plant to touch.

the response of a plant to gravity.

LESSON 1: Inheritance

Inheritance When living things reproduce, they pass on characteristics to their offspring Traits: characteristics, like hair color or height phenotype of a trait is how the trait appears, or is expressed Examples eye colour

Heredity is the passing of traits from parents to offspring. For example, you and your brother might have blue eyes even though both of your parents have brown eyes.

Genetics is the study of how traits are passed from parents to offspring

Self-pollination، Cross-pollination

occurs when pollen from one plant lands occurs when pollen from one plant on the pistil of a flower on the same plant reaches the pistil of a flower on a

different plant

Mendel is known as the father of genetics. • Mendel allowed one group of flowers to self-pollinate. • With another group, he cross-pollinated the plants himself. • Mendel began with plants that were true breeding for the trait that he would test.

When a true-breeding plant self-pollinates, it always produces offspring with traits that match the parent

Punnett Squares The female parent plant is tall – TT. The male parent plant is short – tt. self-pollinating, meaning the F1 genotype is crossed with itself.

First Generation، Second Generation

tall : short = 3 : 1 TT : Tt : tt = 1 : 2 : 1

A dominant trait، A recessive trait

is a genetic factor that blocks another genetic factor.

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

is seen when offspring have either one or is seen only when two recessive genetic

two dominant factors

factors are present in offspring

Purple flowers، White flowers

T = dominant alleles.

t = recessive alleles

What controls traits? Scientists discovered that inside each cell’s nucleus a threadlike structures called chromosomes.

• chromosomes contain genetic information that controls traits • chromosomes exist in pairs—one chromosome from each parent • Each chromosome can have information about hundreds or thousands of traits

A gene is a section on a chromosome that has genetic information for one trait

• A gene example like flower color • A gene is similar to Mendel’s “factors” • The genes on each chromosome can be the same or different, such as purple or

white for pea flower color Alleles are the different forms of a gene. Pea plants can have two purple alleles, two white alleles, or one of each allele. The two alleles that control the phenotype of a trait are called the trait’s genotype

A pedigree shows phenotypes of genetically related family members

Pedigree functions 1. Shows inherited traits. 2. Helps to determine genotype and phenotype. 3. shows relationships between family members.

Pedigree The shapes in a pedigree represent different things:

• a square represents a male • a circle represents a female • a colored square represents a male affected by

a genetic condition • a colored circle represents a female affected by

a genetic condition