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Stored in the Nucleus Determines the nature of each cell in the body and how it will function Made up of nucleotides
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Gregor Mendal – discovered heredity is transmitted in discrete “units” later called genes.
James Watson and Francis Crick – showed DNA is a double helix
Stored in the Nucleus Determines the nature of each cell in the body and how it will function Made up of nucleotides
C = cytosine G = guanine T = thymine A = adenine
4 bases: adenine can only
pair with thymine (AT)
cytosine can only pair with guanine (CG)
The combination of base pairs cannot vary p. 172
1. Which side of the ladder each base comes from2. The order in which the base pairs occur along
the ladder3. The overall number of base pairs
These variations account for differences between species.
All organisms use just these 4 bases, but with different numbers and arrangements
Uncondensed DNA
Chromosome
P 176
Condensed DNA Rod shaped
Each sperm and each egg (gametes) contains 23 chromosomes.
The chromosomes contain genes (a certain length of the chromosome).
The fertilized egg (zygote) and all the body cells that develop from it (except the sperm cells and the egg) contain 46 chromosomes.
Two types1. Autosomes
22 pairs numbered from largest to smallest.
2. Sex chromosomes: 1 pair (23rd pair)
XX in females XY in males
Karotype: picture of chromosomes
P. 177
Question: A liver cell from a human male has:
A) 22 pairs of autosomes, an X and a Y chromosome.
B) 22 pairs of autosomes and two X chromosomes. C) 46 pairs of autosomes, an X and a Y
chromosome. D) 23 pairs of autosomes and two X chromosomes. E) 23 pairs of autosomes, an X and a Y
chromosome.
Answer: A
Each of us has two sets of chromosomes (homologous pairs) one from our mother and one from our father
Each homologous pair contains lengths of genetic information (genes)
Many matched pairs of genes are not exactly alike (alleles)
Differences in our genes account for our uniqueness (green eyes vs. blue eyes)
Genes are a recipe. Alleles are different forms of the same recipe (e.g. chocolate cake and vanilla cake)
23 Pairs = 46 chromosomes total in every cell of your body (except egg and sperm)
HOMOLOGOUS PAIRS
Gene for eye color (blue)
Gene for eye color (green)
allele
Basic unit of genetic information Determine nature and the function of
the cell. The human genes (about 120,000) are
referred to as the human genome. A genome is the full set of genes in
each cell of an organism.
A nuclear enzyme attaches to a segment of DNA causing nucleotide bonds to separate.
Transcription occurs resulting in messenger RNA (mRNA). T is now U (uracil)
Transfer RNA (tRNA) initiates translation into amino acid.
Ribosomes move along the RNA bonding amino acids into polypeptide chains which make proteins.
mRNA
tRNA
NOTE TO STUDENTS: During the cell lecture we learned a part of this process, now we are just inserting one more step (translation using tRNA to tell the ribosome in the right language how to make proteins)
1. Transcription: the transfer of information from a DNA molecule into mRNA molecule.
2. Translation: the transfer of information from an RNA molecule into a Polypeptide, in which language of the nucleic acids is translated into that of amino acids.
Transcription and Translation
DNA staircase unwinds and two chains separate
each chain attracts new biochemical material from the cell to synthesize a new and complementary chain
Ultimately a new cell is formed Process is known as MITOSIS
In the first step of mitosis, all chromosomes are copied, so that instead of 2 copies, the cell briefly has 4 copies of each chromosome.
Shortly afterwards, the cell divides in half, resulting in two cells each has a complete copy of the genetic information.
These cells grow larger and eventually undergo mitosis.
Hint: Mitosis happens in “my toes” and my liver and my mouth etc.
MITOSIS
Homologous pair copied
Gametes: Sex cells (ovum or sperm)
Diploid cells: Cells having 2 copies of each chromosome
Haploid gametes: Gametes having 1 copy of each
chromosome
testicles and ovaries. A diploid cell (having 2 copies of each
chromosome) undergoes a special form of cell division to create haploid gametes (having 1 copy of each chromosome).
An egg and a sperm fuse together to form a new diploid cell called zygote (a process called fertilization).
Meiosis
Mitosis: each cell divides and duplicates itself exactly (46 chromosomes in each cell)
Meiosis: How reproductive cells (eggs and sperm) are produced Results in gametes, cells that contain only
23 chromosomes
Austrian Monk Mathematical principles Classical Genetics
Garden Pea as a model “Basic units” in pairs
p. 210
Example: Pea is wrinkled or smooth
Sexually Reproducing Organism Cross-Pollination (2 different plants) Self-Pollination (same plant)
The seeds in a pod of one of Mendel's pea plants are each the result of a separate fertilization event
Self-pollination occurs as pollen from the anthers falls on the stigma.
1
4
3
2
male anthers
ovaries
Seeds in ovary(peas in pod)
Female stigma
pollination = fertilization
Pollen carry sperm
Pollen falls
Parent generation
(yellow seeds) (green seeds)1
3 2cross-pollination
offspring(yellow seeds)
x
How to cross-pollinate: Mendel’s method
Cross pollinate Wait for Mature plant to
develop Observe characteristics
Phenotype – The observable physical characteristics of an organism, as determined by genetic makeup
Genotype - The combination of alleles located on homologous chromosomes that determines a specific characteristic or trait.
Dominant – when two different alleles are present, the one that is expressed. (Usually represented with a capital letter)
Recessive - when two different alleles are present, the one that is not expressed. (Usually represented with a lower case letter)
Homozygous - with identical alleles at the same locus (location) on homologous chromosomes. (e.g. BB or bb)
Heterozygous - with two different alleles at the same locus on homologous chromosomes. (e.g. Bb)
Monohybrid Cross True-breeding stocks (homozygous)
P (Parental) generation F1
first filial generation
Mendel’s Crosses
Uses letters to represent genes Capital letter denotes dominant gene
and lowercase letter denotes recessive E.g. a tall plant is dominant to a short
Use “T” to represent tall Use “t” to represent short (not s)
HOW TO READ A PUNNETT SQUARE
female gametes
P p P p
P
p
P
pmal
e ga
met
es
pp Pp
1 2
YYYY
YY YY yyyyyyyy
Y Y y y
Y Y y y
Y
Y yy
Yy
YyYy
Yy
YyYy
Yy Yy
female male
female
gamete
s malegametes
possible outcomes in fertilization
P generation
1
2
3
4
5 F1 generation
Question Cross an F1 heterozygous yellow pea with a F1 Heterozygous yellow pea
Y y
Y
y
YY Yy
Yy yy
Genotypic ratio of offspring?
Phenotypic ratio of offspring?
YY
yy
Yy Yy
y y
Y Y
YY
yy
Yy Yy
YY Yy Yy yy
yellow green
threegenotypes
twophenotypes
Y Y
y y
Heterozygous
Homozygous
Applied Mathematical Principles
dominantallele
recessiveallele
maternal paternal maternal paternalmaternal paternal
homozygousdominant heterozygous homozygous
recessive
yellow seeds yellow seeds green seeds
Yy
YYYy Yy
yy
“pure” green
F1 generation
F2 generation
self-pollination
“pure” yellowmixed
YyYY
Yy
yy
YY yyYy
YY F3 generation
YYYY
YYYY
YYYy Yy
yy
yy
yyyyyy
Yy
YYYy
yy yy
Heterozygous or Homozygous?AA _____Ee ____Ii _____mm _____ In guinea pigs, the allele for short hair is
dominant. What genotype would a heterozygous short haired guinea pig have? _______
A heterozygous round seeded plant is crossed with a homozygous round seeded plant. (Round is dominant to wrinkled)
What percentage of the offspring will be homozygous dominant (RR)?
A homozygous round seeded plant is crossed with a homozygous wrinkled seeded plant. What are the genotypes of the
parents? What percentage of the offspring
will also be homozygous?
Questions:
P generation
smoothyellow
wrinkled green
cross-pollinationx
F1 generation
100% smooth yellowself-fertilization
F2 generation
3159
1013
1083
321
smoothyellow
wrinkledyellow
smoothgreen
wrinkledgreen
: : :
Dihybrid Cross• 2 characters
F1 cross with F1
SY Sy sY sy
SY
Sy
sY
sy
SSYY SSYy SsYy SsYy
SSYy SSyy SsYy Ssyy
SsYY SsYy ssYY ssYy
SsYy Ssyy ssYy ssyy
Phenotypic ratio?
P generation
SSYY ssyy
SY sygametes gametes
F1 generation
100% SsYy
F2 generationPollen
EggSY Sy sY sy
SY
Sy
sY
sy
x
SS YY
SS Yy
Ss YY
Ss Yy
SS Yy Ss YY Ss Yy
SS yy Ss Yy Ss yy
Ss Yy ss YY ss Yy
Ss yy ss Yy ss yy
Who are the major players and what did they do?
DNA: what is it? What is it made from? Nucleotide bases: For DNA, for RNA?
What are they? How are they matched? DNA replication, transcription,
translation? What can vary in DNA? What is a Karotype? What are chromosomes? How many do
we have in our cells?
What are genes? Alleles? What is a genome? What are mitosis and meiosis? Which
cells undergo which process. What are the final results?
What are genotype, phenotype, homozygous, heterozygous, dominant, recessive? Example? Recognize?
What is the P and F1 generation?
What are the products of a monohybrid cross? A dihybrid cross? Ratios?
Punnett squares