Transcript Heredity Notes The passing of traits from parents to

Heredity- review, notes
• Heredity Notes
The passing of traits from parents to
offspring is heredity.
• Every organism is identified by its
characteristics or traits.
• Some traits you can see: eye color, shape
of ear, skin color etc. Some traits involve
how the body works: color blindness,
immunity controllers.
• You are born with a code that contains
directions for how you will look and how
your body will work. You inherited this
code from your parents. The code is
found inside the chromosomes located in
the nucleus of the cell. The chromosomes
are made of deoxyribo nucleic acid
(DNA).
• DNA holds the code for thousands of traits
by its unique shape- a ladder. The sides
of the ladder are made of a phosphate
group and a deoxyribose sugar group.
The rungs of the ladder are made of four
nitrogen bases- adenine, thymine,
cytosine and guanine.
• The order in which the bases are
arranged ‘spell’ a message for each trait.
A GENE is the message for the trait!
• A chromosome is made up of a string
of genes which is composed of DNA.
Chromosomes normally appear in pairsthey have the same appearance and
length and the same type of genes.
• Every species has a certain number of
chromosomes- humans- 46 (23 pairs),
bats- 44 (22 pairs), chickens- 78 (36
pairs), goats- 60 (30 pairs).
• For organisms that have two parents,
genes are inherited from each parent.
Humans get 23 chromosomes from the
female, 23 chromosomes from the male,
to combine to form the offspring with 46
chromosomes..
• The reproductive cells (the egg and the
sperm) then have half the number of
chromosomes as the other cells in an
organism. The process where
reproductive cells are made is called
MEIOSIS.
• When the sperm and egg meet in human
reproduction the results are up to chancewith 23 pairs of chromosomes matching
up, there are over 1,000,000 different
combinations possible. You will never be
identical to a brother or sister born at a
different time.
• The study of inheritance is called
genetics. An Austrian named Gregor
Mendel studied pea plants- he found that
pea plants are either tall or short. He
experimented with these plants and
discovered genetics- a tall plant crossed
with a tall plant led to an tall plant, a short
plant crossed with a tall plant led to a tall
plant-
• so the pea plant has a dominant gene for
tallness. The tall gene will always
overpower the short gene. The pea plant
has a recessive gene for shortness.
• The easy way to determine offspring of
parents is to use a punnett square.
• Phenotype- the physical appearance of offspring
• The phenotypes will be described as the traits
themselves (tall or short)
• Genotype- the gene combinations of offspring
• The genotypes can be described as…
• Heterozygous (one of each)- Tt (also called hybrid)
• Homozygous (same) TT, tt (also called purebred)
• Not all traits have dominant and recessive
forms- some traits just blend together- exsome flowers- red and white make pink,
and human race.
• Male- Xy chromosomes
• Females- XX chromosomes
• Some genes carry sex-linked traits
because the genes are on a sex
chromosome. The most common example
is color blindness- this is carried on the X
chromosome- if a boy has an X y then he
will be color blind.