Genetics Page 262 First watch - PowerPoint Presentation

Slide1

Genetics

Page 262Slide2

First watch

Crash Course – Heredity

Or

Khanacademy

- Introduction to HereditySlide3

Genetics

Every living thing has a set of characteristics inherited from its parents (sexual reproduction) or parent (asexual reproduction).

Genetics

is the study of heredity.Slide4

Grego

Mendal’s

work was important to our understanding of biological inheritance

born 1822

Austrian monk

lived in a monastery

taught school

looked after the monastery’s garden.

In this garden, he did the work that would change biology forever.Slide5
Slide6

Observing his pea plants, Mendel knew that:

-the anthers of each flower produced pollen which contained the sperm.

-the female portion of the flower produces the egg cells.Slide7
Slide8

Remember that:

During

sexual reproduction,

male and female gametes join and a nucleus containing both sets of genetic information is formed, a process known as

fertilization.

Fertilization

produces a new cell, a

zygote

, which develops into a tiny embryo. With flowering plants, this embryo is encased in a seed.Slide9

Pea plants usually

self-pollinate

, meaning that they have a single parent

. The pollen fertilizes the egg of the same plant.

Self-pollinating plants are called

true breeding

plants. They produce

offspring identical to themselves.Slide10

Mendel’s Pea Plants

Mendel observed that some of his pea plants were tall, others short;

some had smooth pods, some wrinkled;

some had yellow pods, some green;

some had round peas, some wrinkled;

some had green peas, some white;

some had flowers in an axial position, some terminal;

some had yellow

cotelydons

, some green.

Each offspring always had the same traits as its parent. Slide11

Mendel’s Experiments

Mendel wanted to see what would happen if he produced seeds by fertilizing the eggs from one plant with the pollen from another plant with different traits.

He removed the pollen-producing parts of one plant and dusted pollen from another plant on the stigma (check the diagram in previous slide).

Mendel

cross-pollinated

the pea plants. Slide12

Mendel studied 7 different pea plant traits.

A

trait

is a specific characteristic that varies from one individual to another.

                       Slide13
Slide14

Genes

are the molecular

factors (pieces of code along DNA)that determine traits.

The different forms of a gene are called

alleles.

(In peas, genes can occur in two contrasting forms. i.e. yellow pods/ green pods)

Slide15

Know this terminology

P

: Each original pair of plants (the parental generation)

F1

: the offspring (first filial) of the P

F2:

the offspring of the F1 Slide16

Hybrids

: The offspring of crosses between parents with different traits

.

Ex. A yellow-podded pea plant that is crossed with a green-podded pea plant.Slide17

Gregor

Mendel concluded 2 things from his experiments:

Heredity is determined by the elements that are contained in the cell contributed by each parent of the organism.

When two characteristics are crossed (as in cross pollination, one of the characteristics is dominant over the other. (this theory turned out not to be applicable in all cases) Slide18

Dominance

Mendel’s

principle of dominance

states that

:

some alleles are dominant and some are recessive.

An organism with a dominant allele for a specific trait will always exhibit that form of the trait.

An organism with a recessive allele for a specific trait will only exhibit that trait if the dominant allele is not present. (2 recessive alleles)Slide19

Mendel came to these

conclusions

because of the inferences he made based on the observations from his pea plant experiments

.

Using the letter

T for

tall, and t for short, let’s look at his results.

First cross the pure-breeding

P generation,

all of the plants that are tall with all of the plants that are short.Slide20

Before continuing with this power point, go to the power point on Probability and Punnett Squares and watch

https://www.youtube.com/watch?v=prkHKjfUmMsSlide21

This is a Punnett Square showing the 1

st

cross producing the F

1Slide22

Mendel observed that all the F1 generation were tall. He thought that somehow the short trait had disappeared. Had it?

He then crossed plants from the F1 to produce the F2.Slide23

2

nd

cross producing the F2Slide24

What are the phenotypes of the F2 generation?Slide25

Vocabulary:

Homozygous

: Having the same alleles for a gene. (TT,

tt

)

Heterozygous

: Having different alleles for a gene. (

Tt

)Slide26

Locus

: Location of a particular gene on a chromosome.Slide27
Slide28

Genotype

: Actual genetic makeup. What

kinds of alleles the organism has (Tt, TT,

tt

).

Phenotype

: The

trait displayed

.

(tall

,

short)Slide29

Genome

: Totality of genes. (human genome)

Diploid

: 2n (2 sets of chromosomes)

Haploid

: n (1 set of chromosomes)Slide30

Problem

A homozygous black-coated pig (B) is crossed with a heterozygous pig.

What are the phenotypes of the F1 generation?

What are the possible phenotypes of the F2 generation?Slide31

Problem

Mendel crossed pea plants that were homozygous dominant for round yellow peas with plants that were homozygous recessive for wrinkled green peas.

What did he get in the F

1

generation?Slide32

Watch this video:

How to compare 2 traits at the same time - Dihybrid crossesSlide33

Dihybrid cross FSlide34

Dihybrid cross F+Slide35

SegregationSlide36

Segregation

is the separation of alleles during gamete formation.Slide37

The Principle of Independent Assortment States:

genes

for different traits can segregate independently during the formation of gametes. Independent assortment helps to account for the many variations observed in plants, animals, and other organisms.Slide38

A cross of an individual with a dominant phenotype to a homozygous recessive individual in order to find out its genotype is called a

testcross.Slide39

Genetic variation "reshuffling the genes" comes from several sources with each meiosis

and fertilization

like a 'roll of the dice’- so no two individuals are alike! Slide40

Sources of genetic variation:

1. Crossing Over

at prophase I

2. Independent assortment

: Homologues line up or "shuffle" randomly on the metaphase plate in Meiosis I.

With 23 chromosomes assorting independently, there are

2^23

, or

8 million

, possible assortments of chromosomes inherited for every cell!!

3. Random fertilization

: The ovum has

8 million

possible chromosome combinations, so does the sperm cell.

8 million

x

8 million

=

64 trillion possible diploid combinations

in EACH AND EVERY zygote!

In other words,

you're unique

...(...just like everyone else.....).Slide41

Google “genetics problems”. Choose this website:

http://www.k-state.edu/biology/pob/genetics/intro.

htm

Do

the following questions online:

a. The Formation of Gametes 1, 2, 3

b. Monohybrid Crosses 1, 2, 3, 5

c. Dihybrid Crosses 1, 2, 3, 4, 5