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Heredity
CMS Obj.10-14
State Correlation Obj. 2a-2d
DNA (Deoxyribonucleic acid)
• Chemical inside cell that contains
hereditary information
• Controls how an organism will look &
behave
• Shaped like a twisted ladder
• Rungs hold genetic information that is
a pair of bases
DNA Video
Reproduction
• Organisms produce offspring
through the process of
reproduction.
• The purpose is to transfer DNA
• DNA passes from cell to cell in a
process called Mitosis
• Two types of reproduction
–Asexual
–Sexual
Mitosis
•
Process by which a cell divides to
form two new identical cells
– Two main steps:
1. DNA in the nucleus is copied
2. Nucleus Divides into 2 identical
nuclei
• Purpose is for growth, repair, or
asexual reproduction
Asexual Reproduction
• New organisms produced with the same
hereditary information as the parent using the
process of Mitosis (one parent)
• Examples:
– One-celled organisms (bacteria)
– Regeneration: replacing lost body parts (lizard’s
tail)
– Budding: new organism grows out of the old
one (hydra)
– Cloning: make copies of an
organism (grow new plant from
part of another plant)
Asexual Reproduction Video
Sexual Reproduction
• New organisms is produced from the combined
DNA of TWO different cells called sex cells.
– Male is called sperm & Female is called egg
• Fertilization occurs when an egg and sperm
unite to form a new organism with half of each
parent’s DNA
• Plants sexually reproduce from male and
female parts of a flower
• Sex cells are formed by the process of Meiosis
Meiosis
• A double cell division process that
produces 4 new cells called gametes
with half the number of chromosomes as
the original cell
• Human sex cells have 23 chromosomes
Mitosis & Meiosis
Group Time
•Transfer
DNA
Use the following
phrases
to create a
•Nucleus divides twice
double-bubble
map to compare and
•Nucleus divides once
contrast
Mitosis
& Meiosis
•Two
new cells
•New cells identical to original
• four new cells
•Haploid
•New cells have half the genetic information as original
•Starts with one cell
•Produces sex cells
•Reproductive process
•Diploid
MUTATIONS
• A mutation is a change in a gene or
chromosome.
• Occurs because of an error during
mitosis or meiosis or because of
something in the environment.
• Some mutations are beneficial, some
are harmful, and some are neutral.
– Examples: four-leaf clover, seedless
grapes, & albino rabbit
LET’S REVIEW
Complete the following thinking maps
•
•
Mitosis
2 cells
Mitosis
divides once
as
as
• Use a tree map to classify organisms that use
different types of reproduction
Group Time
Use a double-bubble map to compare
and contrast Asexual & Sexual
Reproduction
Genetics:
The study of Inheritance
Heredity
• The passing of traits from
parent to offspring
• Traits: physical characteristics
of an organism
–Example: eye color, hair
color, & height
Passing Traits to Offspring
• Sex cells have 23 chromosomes and the two
sex cells combine to form body cells with 46
chromosomes.
• In fertilization, one sperm joins with one egg.
• The offspring receives half of its genetic
information from its mother and the other half
from its father.
Genetics
• The study of how traits are passed from parent
to offspring by looking at genes
• Genes are small sections of DNA on a
chromosomes that has information about a trait
• Each chromosome has a gene for the same
trait (eye color from mom & eye color from dad)
• Traits are determined by alleles on the
chromosomes
• Each gene of a gene pair is called an allele
• Inherited traits are determined by the alleles on
the chromosome
Group Time
• Use a brace map to show parts of DNA using the
following terms
– Chromosomes
– Gene
– allele
DOMINANT AND RECESSIVE
• Dominant Alleles describe a genetic factor
that is always expressed.
– It prevents a recessive trait from showing
up in offspring.
– Represented by capital letters (B)
• Recessive Alleles describe a genetic factor
that is not always expressed.
– It only expresses itself when both of the
recessive traits are inherited
– Represented by lowercase letters (b)
Group Time
Use a double-bubble map to compare
and contrast Dominant & Recessive
Alleles
INHERITANCE & PASSING TRAITS
Examining & Studying Traits
• Two ways scientist study traits
– Phenotype: outside expression of a gene
• Blue Eyes
– Genotype: the two alleles a person has
inherited that can only be seen on the DNA
• BB, Bb, or bb
• Two categories of genotypes
– Homozygous: inherited two identical alleles
• BB (pure dominant) or bb (pure recessive)
– Heterozygous: inherited two different alleles
• Bb (hybrid)
Group Time
• Use a double-bubble map to compare
and contrast genotype & phenotype
• Use a tree map to classify the
following genotypes:
DD,Dd,dd,ee,LL,Ll,Hh,HH,Ss,tt,
Punnett Squares
• Shows all possible
combinations of alleles that
children can inherit from
parents
• Mom’s genotype for brown
eyes (Bb)
• Dad’s genotype for brown
eyes (Bb)
• Offspring’s Phenotype
– 75% brown, 25% blue
• Offspring’s Genotype
– 25% BB, 50% Bb, 25% bb
B
b
B BB Bb
b
Bb
bb
DOMINANT & RECESSIVE
VARIATIONS
Variations are the different ways that a certain
trait appears.
• These variations would allow one offspring
to have light brown hair & another to have
darker brown hair
Genetic Advantages & Disadvantages
• Selective Breeding organisms for a certain trait
– Pure breeding
• Advantages: allows breeder to have desirable
traits expressed in offspring
• Disadvantages: unfavorable traits can be passed
& lack variety to survive diseases or climate
changes
– Hybrid
• Advantages: has genetic variety to increase
variations that allows species to adapt to climate
changes or recover from diseases
• Disadvantages: traits are uncertain in predicting