Transcript Chapter 3 Section 1

Chapter 3 Section 3
The Cell and Inheritance
Walter Sutton



American scientist
Studied sex cells (egg and
sperm) to determine how
chromosomes are involved
in the formation.
Studied grasshoppers
Sutton’s Work



Grasshoppers have 24
chromosomes in body cells.
Their sex cells (egg and
sperm) each have 12
chromosomes.
Result: egg cell + sperm cell
= fertilized egg with 24
chromosomes
Sutton’s Conclusion



Genes are located on chromosomes
Genes passed from parent to offspring
on chromosomes
Became known as Chromosome Theory
of Inheritance
Human Cells



Human body cells contain 46 chromosomes
(23 pairs)
Sex cells (egg and sperm) contain 23 chromosomes
The 23rd pair of chromosomes determines the sex of
an individual.



Female genotype – XX
Male genotype – XY
Design a Punnett Square to calculate the probability
of a man and woman having a baby girl of baby boy
Karyotype


Definition –
picture of all the
chromosomes in
a cell arranged
in pairs
Is this karyotype
from a male or
female?
Where is there a problem?
Meiosis



Definition – process by which the number
of chromosomes is reduced by half to
form sex cells
Similar to mitosis but the cell divides
twice.
Resulting sex cells have half the amount
of chromosomes as other body cells.
Meiosis vs. Mitosis
Meiosis Video Clip
http://www.youtube.com/watch?v=qCLmR
9-YY7o
Mitosis vs. Meiosis
Create a T chart to compare and contrast mitosis and meoisis for the
following characteristics.







Involved in what type of reproduction
Type of cells which undergo the process
Reason for this process to occur
Stages involves (list all of the stages)
Number of cells produced
Number of chromosomes in the resulting
cells
How does resulting cell compare to the
parent cell genetically?
Mitosis
Meiosis
Reproduction
Asexual
Sexual
Cell Type?
Body cells
Sex cells (Gametes)
Reason?
Replace old cells, add
cells and growth
Prepare cells for
production of new
offspring.
Stages involved
4 stages:
Prophase, Metaphase,
Anaphase, Telophase
8 Stages:
Prophase (I, II),
Metaphase (I, II),
Anaphase (I, II),
Telophase (I, II),
Number of cells
produced
2
4
Number of
chromosomes in
resulting cells?
Full Set (Diploid)
Human = 46
Half set (haploid)
Human = 23
How do daughter cells
Identical DNA (clone)
Different DNA –
Protein Structure
unwind
The Genetic Code

What are the 4 different nitrogen bases in
a DNA molecule? How do they pair?


Adenine pairs with Thymine
Cytosine pairs with Guanine
Base Pairing – The secret to code!!
Adenine pairs with Thymine
Guanine pairs with Cytocine
The Genetic Code

The order of nitrogen bases along a gene
forms a Genetic Code that specifies what
type of protein will be produced.
The Genetic Code
ATTCGGTG
Genes make proteins
Proteins make YOU!!
The Genetic Code (cont.)



What are the building blocks of
protein?
A group of three nitrogen bases
codes for a specific amino acid.
The production of proteins is
called protein synthesis.

Two steps – Transcription and
Translation
Introducing a new player - RNA
DNA vs. RNA - Chart
The Genetic Code
Protein synthesis takes place on the ribosome.
Two types of RNA
Protein Synthesis
http://highered.mcgrawhill.com/sites/0072943696/student_view0/chapter3/
animation__how_translation_works.html
Mutation

Definition – mistake that occurs in one
gene of a chromosome. This causes the
cell to produce an incorrect protein which
results in a different physical trait or
phenotype.
Mutations

Mutations are usually random and can be:




Harmful – causes harm to the organism
Helpful – helps the organism to survive
Neither harmful or helpful.
Mutations can also be caused by
environmental hazards.

These are usually harmful
Mutations
The mice ran away.
Substitution Mutation
Deletion Mutation
Insertion Mutation
The rice ran away.
Thei cera naway.
The migukce ran away.
Steps of Protein Synthesis


DNA “unzips” between the Nitrogen Base
pairs
Genetic info. from DNA is copied by the
mRNA which leaves the nucleus and
attaches to a ribosome in the cytoplasm.
Steps of Protein Synthesis (cont.)


Transfer RNA (tRNA) picks up amino acids
according to the mRNA code of nitrogen
bases.
Each tRNA molecule attaches the amino
acid to the growing protein chain.
(Show overhead diagram and video clip)
Protein Synthesis

The genetic messenger is called
messenger RNA (or mRNA).
mRNA carries the DNA code from the
nucleus out into the cell’s cytoplasm to the
ribosomes where proteins are produced.

This process is called TRANSCRIPTION

Questions


Why can’t DNA leave the nucleus to
produce proteins?
Why is it important for meiosis to occur?
What would happen if human sex cells
had 46 chromosomes instead of 23?