Transcript Heredity and Genes

Ms. Doshi
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Read Chapters 5.1 and 5.2
Do the review worksheet from the website.
Write your answers on a separate piece of
paper or in your notebook.
You have 20 minutes
AND EXTRA PROBLEMS
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The full set of DNA in an individual organism
is called a genome.
One or more unique pieces
of DNA is called a
chromosome.
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circular in prokaryotes
linear in eukaryotes
A specific sequence about
30, 000 bases long is a gene.
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Heredity – the passing of traits from parents to
offspring .
It has been estimated that more than 8 million
combinations are possible from the 23
chromosomes inherited from each parent. The
more than 8 million combinations from each
parent will produce more than (8 × 106)(8 ×
106) or 6.4 × 1013 (64 trillion) possible
combinations for offspring. Your genetic
makeup is one of those combinations.
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alleles: two or more alternate forms of a gene.
The alleles are located at the same position on
one of the pairs of homologous chromosomes.
dominant: the allele that, if present, is
ALWAYS expressed. Example: TT or Tt
recessive: the allele that is expressed only if it
is not in the presence of the dominant allele i.e.
if the individual is homozygous for the
recessive allele. Example: tt
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homozygous: describes an individual that carries
two of the same alleles for a given characteristic
Example: The homozygous condition for a tallstem plant would be TT. The homozygous
condition for a short-stem plant would be tt.
heterozygous: describes an individual that carries
two different alleles for a given characteristic
Example: The only heterozygous condition
possible for stem length in a garden pea is Tt.
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Punnett square: a diagram that summarizes
every possible combination of each allele from
each parent; a tool for determining the
probability of a single offspring having a
particular genotype
Monohybrid Cross: a cross designed to study
the inheritance of only one trait
Examples of one trait: color of eyes, color of hair,
height of plants.
 genotype: the code carried by the organism
 phenotype: the physical characteristics of the
organism seen, as a result of the code.
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In humans brown eyes are dominant over blue
eyes. What type of offspring would you expect
if you crossed a heterozygous brown eyed
person to a heterozygous brown eyed person?
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In humans tongue rolling is dominant to nontongue rolling. What would be the expected
type of offspring if a homozygous tongue roller
was crossed to a heterozygous tongue roller?
In a certain plant yellow fruit is dominant to
white fruit. A heterozygous plant with
yellow fruit is crossed with a plant with white
fruit. Determine the probable offspring.
Tall plants are dominant to short plants in the
garden pea plant. Cross a heterozygous
tall plant to a heterozygous tall plant.
Now..It’s your turn.
Do Worksheet 1 from the website.
In humans, genes make up
only 2% of DNA.
These genes all code for
proteins.
The rest is “non coding
DNA” which may or may
not have a purpose. We
don’t know what it does
yet.
So, not all DNA codes for
proteins.
ONLY genes code for
proteins.
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regions of DNA are in
color in the picture.
regions of DNA that
do not code for
proteins are in gray.
75% of non-coding
regions of DNA are
between genes .
25% of non coding
regions inside genes
are called introns.
DNA (gene)
In the nucleus
Transcription
mRNA
mRNA leaves nucleus through nuclear pores
In the cytoplasm
Translation
Proteins
DNA (gene)
In the cytoplasm
Transcription
mRNA
In the cytoplasm
Translation
Proteins
1.
2.
3.
4.
5.
6.
7.
8.
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10.
_______% of fruit fly DNA codes for genes.
_______% of human DNA codes for genes.
Non coding DNA inside genes are called ________.
What is transcription?
What is translation?
In what parts of the cell does transcription and
translation occur in prokaryotes?
In what parts of the cell does transcription and
translation occur in eukaryotes?
Put in order of amount of DNA (from least to most):
onion, human, salamander, fruit fly.
Put in order of percentage of coding DNA (from least
to most): E.coli, human, round worm, fruit fly
What enzyme is used in transcription?
Watch this video:
http://www.youtube.com/watch?v=WsofH466lqk
Transcription:
Recognize and bind:
The part of the DNA where transcription occurs is the
transcription unit. A promoter site is made: TATA box +
transcription factors. RNA polymerase binds to the promoter site
with other transcription factors. Energy (ATP) is added.
2. Transcribe:
The RNA polymerase starts transcribing the RNA from the DNA.
When transcription starts, the transcription factors are released.
The RNA is now called mRNA because it is now carrying the
message to make a protein.
3. Terminate:
When the end of the transcription unit is reached (the termination
sequence), the RNA polymerase leaves, and the new strand of
mRNA is released.
1.
Remember:
If DNA has
thymine (T)
adenine (A)
guanine (G)
cytosine (C)
add
add
add
add
mRNA
adenine (A)
uracil (U)
cytosine (C)
guanine (G)
Re-write on board:
nucleotide sequence
DNA
CTTACTAATCTTGACTC
mRNA
GAAUGAUUAGAACUGAG
Watch this video:
http://www.youtube.com/watch?v=5bLEDd-PSTQ
Translation:
Recognize and initiate protein building:
The ribosome and tRNA bind to the AUG initiation (start) site.
AUG codes for Methionine. AUG is always the START sequence
for protein translation. Methionine can be seen on the tRNA.
2. Elongate:
Each 3 bases, after the AUG (start codon) from the mRNA, codes
for an amino acid on the tRNA. These amino acids elongate like a
chain as each tRNA transfers the amino acid from the tRNA in the
P site to the tRNA in the A site.
3. Terminate:
The complex reaches a STOP codon. Everything dissociates and
the polypeptide chain (protein) is made.
1.
Re-write on board:
nucleotide sequence
DNA
CTTACTAATCTTGACTC
mRNA
GAAUGAUUAGAACUGAG
Codon
AUG-AUU-AGA-ACU-GAG
AntiCodon
(tRNA)
Protein
(Amino
Acids)
UAC-UAA-UCU-UGA-CUC
GA START Ile Arg Thr Glu
Try Worksheets 2 and 3 from the website!
Worksheet 3 is a little difficult, but you can do it!