4.1 Living Things Inherit Traits in Patterns

• We know the offspring produced by sexual reproduction have genetic material from two parents

• Offspring get traits from parents

• But not all traits

4.1 Living Things Inherit Traits in Patterns

• Inherited trait

• Acquired Trait• characteristic developed

during life

• characteristic passed down from parents

• born with it

• determined by genes

In the table below, write yes if the trait is the result of heredity or no if it is not.

Trait Result of Heredity?

Blonde hair

Able to speak English

Able to ride a bike

Green eyes

4.1 Living Things Inherit Traits in Patterns

Yes

Yes

No

No

If a mother works out as a body builder for many years, are the chances high that her offspring will inherit strong muscles? Why or why not?

• The offspring has the potential for strong muscles, but a muscle grows if it is worked. The child will have to do the same workouts to get big muscles, he/she will not be born with them.

4.1 Living Things Inherit Traits in Patterns

4.1 Living Things Inherit Traits in Patterns

• Inherited traits are controlled or coded for by genes

• heredity• Passing of genes from

parent to offspring

• genes – unit of heredity that codes for a particular trait

• examples:Eye colorHair color

4.1 Living Things Inherit Traits in Patterns

• There are various forms of the same gene

• blue

• Example – • Eye color has several variations

• brown

• green

• hazel

• These variations are called alleles

4.1 Living Things Inherit Traits in Patterns

• Example:• Brown or blonde hair

• What is the gene?

• What is the allele?

4.1 Living Things Inherit Traits in Patterns

• When working with heredity, genes are assigned a letter

• The gene would code for hair color and could be represented by the letter H

• Example:• Brown or blonde hair

• So each allele would be a variation of the letter H to represent a variation of the gene

• h = blonde

• H = brown

• Capital letter represent dominant alleles and lower case letters represent recessive alleles

4.1 Living Things Inherit Traits in Patterns

• Dominant – an allele that determines the phenotype of an individual organism when two different copies are present in the genotype

• Recessive – an allele that is not expressed when combined with a dominant form of a gene. It is only expressed in the phenotype when both alleles present in the genotype are recessive

• If a dominant allele is present, the trait of the dominant allele shows. Whether one or two dominant alleles are present

4.1 Living Things Inherit Traits in Patterns

• If there is no dominant allele, and both alleles present are recessive, then the recessive trait shows

Why are some parents’ traits expressed in their offspring while others are not?

• Dominant traits are expressed even if only one allele codes for it.

4.1 Living Things Inherit Traits in Patterns

If a trait is recessive, both alleles must be recessive for it to show in the phenotype.

• The trait that shows as a result of the genotype is the phenotype

• Example -

• The combination of alleles is the genotype

• Eye color is represented by the letter E

e = blueE = brown

4.1 Living Things Inherit Traits in Patterns

Genotypes EE Ee ee

The resulting phenotypes

Brown eyes

Brown eyes

Blue eyes

• 2 dominant alleles =

4.1 Living Things Inherit Traits in Patterns

dominant phenotype

• 1 dominant allele• and 1 recessive allele = dominant phenotype

• 2 recessive alleles = recessive phenotype

A science student crosses a purebred regular height pea plant with a dwarf height plant. Four new pea plants are grown. Draw the four pea plants in the space below. Be sure to make them the right height.

4.1 Living Things Inherit Traits in Patterns

4.2 Patterns of Heredity can be Predicted

Unit AChapter 4

Punnett Squares• chart used to show all of the ways genes from two

parents can combine and be passed on to offspring• shows possible outcomes for inheritance - the

possible combinations of parents allelesthe top part shows one parent’s alleles for a trait

the side shows the other parent’s alleles for a trait

H

H

h

h

H

HH

H

h h

H

H

h

h

1. How is the symbol for each allele the same?

• Each allele for a trait is symbolized by the same letter

2. How can you tell which allele is dominant?

• Dominant alleles are symbolized by capital letters.

3. How can you tell which allele is recessive?

• Recessive alleles are symbolized by lower case letters.

4. Which trait is dominant here?

• Regular height (H)

5. Which trait is recessive here?

• Dwarf height (h)

6. What does each box show?

• The alleles of one possible offspring

4.3 Meiosis is a special form of cell division• Sexual reproduction involves two

parents

• Each parent produces specialized cells that contain half the amount of genetic material a cells needs

• The specialized cells contain one allele for each gene and are called haploid cells

• sperm – gamete of the male

• egg – gamete of the female• also known as gametes

• contain half the usual number of chromosomes (one chromosome from each pair of chromosomes)

• Haploid cells 4.3 Meiosis is a special form of cell division

• 1n cells

4.3 Meiosis is a special form of cell division

• The cell resulting from a sperm and egg combining has a full set of DNA

• They have two alleles per gene and are called diploid cells

• contains the full number of chromosomes (both chromosomes in a pair)

• Diploid cells

• 2n cells

4.3 Meiosis is a special form of cell division

• Example: In humans

• haploid cells have 23 chromosomes

• diploid cells have 46 chromosomes

4.3 Meiosis is a special form of cell division

• Meiosis• special kind of cell division that

produces haploid cells• involves two divisions of a single cell

• takes place only in reproductive tissues of an organism

• necessary for sexual reproduction

4.3 Meiosis is a special form of cell division

• Meiosis• during sexual reproduction, the gametes

(1n) combine to become a 2n cell that grows into the offspring:

• the new cell that is formed has half its genetic information from its mother and half from its father

• fertilization – sperm and egg combine to form one new cell

genetic information

from the mother

combines with

genetic information

from the father

to form A new cell

4.3 Meiosis is a special form of cell division

Meiosis IMeiosis II