Meiosis and Reproduction

Types of Reproduction

• Asexual Reproduction – production of offspring that requires only one parent; all the genetic materials come from the one parent, so offspring are identical

• Sexual Reproduction – production of offspring (kids) that requires one male and one female parent; chromosomes come from both parents

Meiosis • Meiosis – the process by which sex cells

are made

• So we’re not talking about our body cells any more they get Mitosis were talking about GAMETES. What is a

Gamete?

What is a Gamete?

GAMETES• Gametes – sex cells

• Male sex cell is sperm; female sex cell is egg

• The male and female sex cells unite (come together) in sexual reproduction to produce an organism, this process is called fertilization

Lets Label the Pictures

Sperm Egg Fertilization

Important Chromosome Information

• Chromosomes are thread-like structures found in the nucleus that contain DNA (genetic material)

• Chromosomes occur in Pairs–Homologous Chromosomes – chromosomes

that have the same shape and size and carry information for the same traits (genes)

- For every chromosome an organism has, there is another one just like it

Replication

This one is from Pa And this one is from Ma

Important Info Continued

Humans have 46 total chromosomes

• Humans have 23 different chromosomes (since they all have a matching pair)

• In all of our body cells (ex. skin cells, heart cells, liver cells, ect.) we have 46 total chromosomes

• The chromosomes that we have 1/2 came from our mom and 1/2 came from our dad

Chromosomes in Gametes (Sex Cells)

• If we make egg and sperm with 46 chromosomes each, how many chromosomes would our kids have when the sperm and egg unite?

• 92• What must we do with the number of

chromosomes in our gametes (sperm and egg) to make sure our kids only have 46 chromosomes?

• Cut the number in half

How many chromosomes are in the daughter cells (sex cells)? 1

How many daughter cells (sex cells) are produced? 4

chromosomes do not line up single file in the middle, homologous pairs line up side-by-side

How many chromosomes are in the parent cell? 2

(Look here) Where have I seen this?

Mitosis vs. Meiosis• occurs in body cells

• involves only one division

• Daughter cells look Identical to parent cells

• have same # of chromosomes in daughter cells as parent

• 2 daughter cells produced

• occurs in sex cells

• involves two divisions

• Daughter cells are NOT identical to parent cells

• have half # of chromosomes in daughter cells as parent

• 4 daughter cells are produced

ReproductionThe Process of Organisms making more

organisms like themselves

2 Types

• Asexual Reproduction – production of offspring that requires only one Parent

• Sexual Reproduction – Production of offspring that requires 2 parents one Male and one Female Parent

Asexual Reproduction - Involves only one parent• Parent goes through the Cell Cycle

and end up with offspring (kids)

• Offspring are Identical to the Parent

• Involves only the process of

Mitosis

Asexual reproduction in single-celled organisms

• Occurs by process of cell division and offspring are genetically identical to parent cell

Ex. of Cell Division• Binary Fission –

when a cell divides into two identical cells that are equal in size

• Occurs in bacteria

Ex. of Cell Division• Budding –

when a cell divides into two identical cells that are unequal in size

• Occurs in

Yeast

This is Cloning NOT Budding

Asexual reproduction in Multi-cellular organisms

• Some multi-cellular organisms can reproduce asexually by breaking off a body part. The body part then develops into a new organism

• The new organism is genetically identical to the parent organism

Example• Plant Propagation – when parts

on a plant (such as leaves or roots) are used to grow another plant

Example• Regeneration – when part of

an animal is used to develop into an entire new animal–Ex. Sea Stars

Sexual Reproduction

- requires 2 parents• Offspring are NOT genetically

identical to parent

• ½ genetic material comes from male and ½ comes from femaleDAD MOM

Necessary Requirements

• In order for sexual reproduction to be successful, organisms need to make gametes that have half the # of chromosomes as a normal cell

reason: the gamete will combine with another gamete to make an organism

Gametes• Sex cells (cells involved in sexual

reproduction)

Sperm in male & Egg in female

They only have 23 chromosomes in each. They are no longer paired

How are gametes made?

• By a process called Meiosis

MeiosisParent Cell

4Gametes