DNA AND IT’S

REPLICATION• What is DNA, and how does it make more of

itself?

• How does DNA get passed on to the next

generation?

7.14B compare the results of uniform or diverse offspring from sexual

reproduction or asexual reproduction

7.14C recognize that inherited traits of individuals are governed in the

genetic material found in the genes within chromosomes in the nucleus

DNA Structure

DNA consists of two molecules that are arranged into a ladder-like structure called a Double Helix.

A molecule of DNA is made up of millions of tiny subunits called Nucleotides.

Each nucleotide consists of:

1. Phosphate group

2. Pentose sugar

3. Nitrogenous base

Nucleotides – look like this:

Phosphate

Pentose

Sugar

Nitrogenous

Base

Draw this!

Nucleotides

The phosphate and sugar

form the backbone of the DNA molecule, whereas the

bases form the “rungs”.

There are four types of nitrogenous bases.

Phosphate

Sugar

bases

4 Types of Nucleotides

A

Adenine

T

Thymine

G

Guanine

C

Cytosine

Nucleotides

Each base will only bond with one other specific

base.

Adenine (A)

Thymine (T)

Cytosine (C)

Guanine (G)

Form a base pair.

Form a base pair.

G

G

A

T

T

A

A

C

T

G

C

A

T

C

First they pair up,

Then the bonding

occurs.

This is what

makes the ladder

formation!

DNA

Structure

Because of this

complementary

base pairing, the

order of the bases

in one strand

determines the

order of the bases

in the other strand.

DNA Structure

You learned before that a gene is the part of your DNA that influences a trait. It is also a section of DNA that codes for a protein.

Each unique gene has a unique sequence of bases.

This unique sequence of bases will code for the production of a unique protein.

It is these proteins and combination of proteins that give us a unique phenotypes.

Recall that Phenotypes are…

all the observable characteristics of an organism,

such as shape, size, color of eyes and hair

This is how DNA = YOU!

Who discovered the model of DNA?

In 1953, Frances Crick and James Watson modeled the chemical structure of DNA.

The order of four molecules codes for every part and kind of life.

Life is incredibly diverse!

Where is the DNA?

In each cell, there is a nucleus (in eukaryotic cells)

And in the nucleus is the genetic material, the DNA

DNA is too long to fit into that tiny cell; if you were to string out one cell’s DNA, it would be 6 feet long.

So, chromosomes “package” the DNA so it fits!

How DNA is packaged (1 min.)

How does DNA replicate?

The two strands of DNA must be separated and

copied.

One protein separates the two strands of DNA.

Another protein brings the correct new base to pair

with the existing base, matching them.

DNA Replication

In this way, two DNA

strands are formed from

one (the first one is copied).

Each new DNA double

helix has one old strand

(the parent strand) and

one new strand (the

daughter strand).

Daughter Strand

Daughter

Strand

Parent

Strands

Your DNA

All of the DNA in a cell of a human is called the

“human genome”.

The human genome has over 3.2 billion base

pairs.

Humans have 23 pairs of chromosomes

DNA - Videos

https://www.youtube.com/watch?v=zwibgNGe4aY

https://www.youtube.com/watch?v=5qSrmeiWsuc

https://www.youtube.com/watch?v=zdDkiRw1PdU

(short)

TYPES OF

REPRODUCTIONAsexual Reproduction

Sexual Reproduction

Purpose of Reproduction

To make sure a species can continue

To make new cells

Asexual Reproduction

New organism is produced from ONE parent

Offspring are IDENTICAL to the parent and

each other.

Genetic material is donated from that one

parent. (so is there variety in the genes?)

Very common in plants; less so in animals

Examples of Asexual Reproduction

Budding – living organisms make

offspring that form from

outgrowths (buds) on the bodies of

the parent.

some organisms like hydra and

corral can form a mass of cells

called a “bud”.

That bud specializes to form a new

organism on the side of the parent.

It will drop off and become its own

organism.

Examples of Asexual Reproduction

Vegetative propagation – some plants can grow whole

new plants from divided parts

It will drop off and become its own organism.

Ex. spider plant

Examples of Asexual Reproduction

Spores – seed like capsules of DNA

and tissue that can grow under the

right conditions.

They are produced by nonflowering

plants, bacteria, fungi, and algae, and

are often able to travel over long

distances.

Ex. mushrooms, molds

Examples of Asexual Reproduction

Regeneration –some organisms (starfish and the salamander) can replace an injured or lost part, and many plants are capable of total regeneration (the formation of a whole individual from a single fragment such as a stem, root, or leaf)

Examples of Asexual Reproduction

Binary Fission -

The process in

which a parent

cell splits into

two daughter

cells of

approximately

equal size.

Advantages and Disadvantages

Asexual Reproduction

Advantages:

o Faster and easier – no partner needed

o Less chance of mutation – less steps to follow,

so less chance things can go wrong

• Disadvantages:

o Less genetic diversity (parents = to

offspring) means less chance of survival if

the environment changes

Sexual Reproduction

Sexual Reproduction - the production of new living organisms by combining genetic information from two individuals of different types (sexes).

Genetic material is donated from two parents

The process is called fertilization

Half of the genes for each trait come from the male parent and half from the female parent.

Offspring differ from each parent and from each other.

Parents typically care for their offspring.

There are less offspring (in general)

Examples of Sexual Reproduction

Pollination - Plants that rely on flowers for reproduction

are also very dependent on outside help such as insects

and animals.

A bee might go to one flower and get a little pollen on

its back. If it goes to another flower of the same

species, that pollen can land on the stigma. If

successful, an embryo and seed/fruit develop

respectively.

https://www.youtube.com/watch?v=1OFF2qYvLag

Sexual Reproduction examples:

Sexual reproduction in animals

Animal male gamete is called sperm. Sperm is a

mobile cell that moves using its 'tail', called

flagellum. Female gamete is called an ovum. It

does not move and it is much larger than sperm

The egg and sperm combine for fertilization.

Advantages and Disadvantages of

Sexual Reproduction

Advantages:

Greater genetic diversity due to large number of gene combinations that can occur (think increased biodiversity)

Disadvantages:

It is a slow process, and a greater chance of mutations in the DNA replication process

Energy is expended finding a mate

Only works in complex organisms

Important !!!!!!!!!!!

Asexual reproduction results in offspring

that are genetically identical to the

parent organism

Sexual reproduction results in offspring

that are genetically different from the

parent organisms

Your notes should be complete!

Check them for completion and then place them in

your binder.