Chapter 8 - Mendelian Genetics - Biology



Genetics

Why Study Genetics? _______________________________________________________________

I. Terms to Know and Use:

Genetics - _________________________________________________________________________

Heredity - _________________________________________________________________________

II. Gregor Johann Mendel (a.k.a. “Father of Genetics” )

* 1822 to __________ *Austrian __________

* Experimented with __________ *Trained in __________ and __________

III. Garden Pea Experiments (1856 – 1864)

• Were __________ to grow

• Produced a large number of __________

• __________ quickly

• Had both __________ and __________ parts

A. The Problem

T.A. Knight, a scientist, saw that if he crossed

pure bred pure bred

purple pea plant (P) x white pea plant (P)

________ the offspring would be purple (F1).

If he then crossed the purple (F1) offspring:

hybrid hybrid

purple pea plant (F1) x purple pea plant (F1)

_______

offspring are purple (F2) & ________ white (F2).

B. Mendel’s Answer

Mendel used __________ along with __________ to explain heredity.

He counted: 705 purple

224 white

Total: 929 pea plants

Thus he discovered a __________ ratio

C. To explain this ratio he came up with the __________ ___ __________

1) Parents transmit “__________” to offspring.

2) Each individual has _____ genes (1 from each parent)

3) Some “__________” are dominant and others recessive.

IV. Lucky or Right On?

Mendel repeated his experiments while observing other traits such as:

•__________ of plant (tall vs. short)

•__________ appearance (inflated vs. constricted)

•__________ color (green vs. yellow)

•__________ texture (round vs. wrinkled)

•__________ color (yellow vs. green)

V. Mendel's Laws of Inheritance

• Law of Segregation - _________________________________________________________

•

•

_

____________________________________________________________________________

•

•

• Law of Independent Assortment - _______________________________________________

____________________________________________________________________________

•

VI. More Terms to Know and Use

Trait - _____________________________________________________________________________

Allele - ____________________________________________________________________________

Gene - ____________________________________________________________________________

Locus - ____________________________________________________________________________

Dominant - _________________________________________________________________________

Recessive - _________________________________________________________________________

Homozygous - ______________________________________________________________________

Heterozygous - ______________________________________________________________________

Genotype - _________________________________________________________________________

Phenotype - ________________________________________________________________________

Monohybrid Cross - __________________________________________________________________

Dihybrid Cross - ____________________________________________________________________

VII. Determining Unknown Genotypes

•How do you know if a dominant phenotype is homozygous (AA) or heterozygous (Aa)?

•Scientists can perform a _______ where they cross the unknown with a recessive (known) phenotype.

VIII. Sex-Linked Traits

• Characteristics that are inherited from genes found on the __________ chromosomes.

Sex-Linked Traits

• Sex Determination

o Females – _________

o Males – _______

• Almost all sex-linked traits are found on the ________ chromosome

• Y chromosome contains very ________ genes and is mainly involved in ______ determination

• It is possible for a female to be a carrier of an X-linked trait, but not _____________ it

• Men will express _________ X-linked traits they inherit

Example: Color Blindness

IIX. Pedigree Charts

• What is a Pedigree Chart?

o Pedigree charts show a record of the family of an individual

o They can be used to study the ________________________ of a hereditary condition

o They are particularly useful when there are ____________ families and a good family record over __________________ generations.

• Studying Human Genetics

o You ______________________ make humans of different types breed together

o Pedigree charts offer an ___________________ way of studying human genetics

o Today genetic engineering has new tools to offer doctors studying genetic diseases

o A genetic counsellor will still use pedigree charts to help determine the distribution of a ______________________ in an affected family

• Symbols Used in Pedigrees

o Normal male:

o Affected male:

o Normal female:

o Affected female:

o Marriage:

o Generations are identified by ________________________

o Individuals in each generation are identified by Arabic numerals numbered from the left

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