Post on 02-Apr-2015
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Big Idea 16: Heredity and Reproduction
Description A. Reproduction is characteristic of living things and is essential for the survival of species.
B. Genetic information is passed from generation to generation by DNA; DNA controls the traits of an organism.
C. Changes in the DNA of an organism can cause changes in traits, and manipulation of DNA in organisms has led to genetically modified organisms.
Benchmark Number & Descriptor
• SC.7.L.16.1• Understand and explain that every organism requires a set of
instructions that specifies its traits, that this hereditary information (DNA) contains genes located in the chromosomes of each cell, and that heredity is the passage of these instructions from one generation to another.
• SC.7.L.16.2• Determine the probabilities for genotype and phenotype combinations
using Punnett Squares and pedigrees.• SC.7.L.16.3• Compare and contrast the general processes of sexual reproduction
requiring meiosis and asexual reproduction requiring mitosis.• SC.7.L.16.4• Recognize and explore the impact of biotechnology (cloning, genetic
engineering, artificial selection) on the individual, society and the environment.
WHO ARE YOU?
DNA• DNA =
Deoxyribonucleic Acid• Traits which are
passed from parents to offspring are carried in DNA.
• DNA is a blueprint for the cells in an organism.
• Without DNA, an organisms traits would never form.
DIRECTIONSGENES
• Pieces of DNA• Carry traits
• Characteristics
• Help pass traits from parent to offspring– You inherit your genes.
• Offspring receive only some genes from parents.
• Genes combine differently, so you look different.
CHROMOSOMES• Genes are located on
chromosomes.– Thousands of genes can be
found on a single chromosome.
• Chromosomes are found in the nucleus of the cells.
• Each type of organism contains a set number of chromosomes.– Humans = 23 Pairs
PUTTING IT ALL TOGETHER
KNOWLEDGE CHECK
1. What does DNA stand for?
2. Where is DNA located?
3. Why is DNA important?
KNOWLEDGE CHECK
1. What does DNA stand for? Deoxyribonucleic Acid
2. Where is DNA located? DNA is located on genes which are carried by chromosomes.
3. Why is DNA important? It’s the blueprint for how organisms are made.
WHY DON’T WE LOOK ALIKE?
What is Heredity?• Heredity is the passing on
of characteristics (traits) from parents to offspring.
• Genetics is the study of heredity.
Gregor Mendel
• WHO: – Austrian monk
• WHAT: – Worked with pea plants and discovered how traits get
passed from generation to generation
• WHEN: – Around 1856
PASSING OF TRAITS• Each gene contains 2 ALLELES
– 1 allele from mom– 1 allele from dad
• Individual alleles are represented by an upper or lowercase letter.
• Some alleles are dominant, and others are recessive.
BLUE = alleleRED = allele
together = gene
TRAITSTYPES OF TRAITS
• The trait that is observed in the offspring is the DOMINANT TRAIT (uppercase).
– It only takes one dominant allele for that trait to be shown.
• The trait that disappears in the offspring is the RECESSIVE TRAIT (lowercase).
– It takes 2 recessive alleles for that trait to be shown.
LETTER COMBINATIONS
• Heterozygous - if the two alleles for a trait are different (Aa)– Also referred to as a hybrid
combination
• Homozygous - if the two alleles for a trait are the same (AA or aa)– Also referred to as a
purebred combination
TRAITSGENOTYPE
• Refers to the letter (allele) combination– TT, Tt. tt
• If a capital letter is present in the letter pair, the dominant trait will be expressed in that organism.
• If 2 lower case letters are paired, the recessive trait will be expressed in that organism.
PHENOTYPE• Refers to the physical
characteristic being expressed
• Uses words/phrases to describe not letters
• Examples: – tall, short– white, black
PUNNETT SQUARES • Tool used to determine
characteristics of offspring• Each box represents the
probability of an offspring receiving a trait.– Example:
• Top outside (Tt) is a gene passed on by the father
• Left outside (tt) is a gene passed on by the mother.
• 4 middle boxes are possible gene combinations an offspring may receive.
T
t
T
t
Tt
Tt
Tt
Tt
T = Tall
t = Short
All offsprings will be tall (all boxes contain the dominant trait for tallness).
PUNNETT SQUARES
• Short hair (L) is dominant to long hair (l) in mice. What is the genotype and phenotype ratio of a heterozygous short-haired mouse crossed with a long-haired mouse?
• Punnett Square: L l
l
l
• Genotype ratio: ½ Ll: ½ ll
• Phenotype ratio: ½ short hair: ½ long hair
Ll ll
Ll ll
PEDIGREE• A chart used to trace
traits throughout a family
• Parts of the chart– Circle = females– Squares = males– Half-filled in/Dotted =
carrier• Have the gene but do
not show signs of it
– Filled-in = affected• Have both the gene
and symptoms of that trait
KNOWLEDGE CHECK
1. What do we call the trait that is observed?
2. What case (upper or lower) is it written in?
3. What about the one that disappears?
4. What case is it written in?
• Trait Tall = Aa • Trait short = aa• Aa x aa5. Complete the Punnett Square.
____ ____
____
____
KNOWLEDGE CHECK
1. What do we call the trait that is observed? Dominant
2. What case (upper or lower) is it written in? Upper
3. What about the one that disappears? Recessive
4. What case is it written in? Lower
• Trait Tall = Aa • Trait short = aa• Aa x aa5. Complete the Punnett
Square.
__A_ __a_
_a__ Aa aa
_a__ Aa aa
HOW DO WE GET ALL THIS STUFF?
REPRODUCTIONSEXUAL
• Primary method of reproduction for the vast majority of visible organisms, including almost all animals and plants
• Characterized by two processes:– meiosis, halving of the
number of chromosomes– fertilization, combination of
two gametes and the restoration of the original number of chromosomes
• Results in increasing genetic diversity of the offspring.
ASEXUAL• A form of reproduction
which does not involve meiosis or fertilization
• Asexual reproduction = one parent.
• The primary form of reproduction for single-celled organisms such as archaea, bacteria, and protists
• Mitosis is the main way of reproduction.
REPRODUCTION
ASEXUAL• MITOSIS
– All forms of asexual reproduction utilize the process of mitosis.
– Begins with one replication (copying of the chromosome material) and one division of the chromosome material
– This results is 2 daughter cells being produced with the same number of and identical chromosomes as in the parent cell.
Asexual reproduction in liverworts: a caducuous phylloid germinating
Mitosis• Interphase
– Normal functions– Upon trigger,
chromosomes & centrioles duplicate.
• Prophase– Early: nuclear envelope
degrades; chromosomes start to condense.
– Late: chromosomes thicken; spindle forms between centrioles
• Metaphase– Spindle fibers attach to
kinetochores.– Chromosomes line up at
cell equator.
sdst.org/shs/apbio/... /mitosis powerpoint.ppt
Mitosis• Anaphase
– Chromatids separate at centromeres
– Chromosomes move to poles.
• Telophase– Nuclear envelope
reforms in each of two daughter cells.
– Cytokinesis separates two new cells.
• Interphase– Daughter cells are
genetically identical to each other and the parent cell but smaller.
sdst.org/shs/apbio/... /mitosis powerpoint.ppt
REPRODUCTION
SEXUAL• MEIOSIS
– Process produces the sex cells
• Contain ½ the chromosomes as the parent
– Since ½ male chromosomes and ½ female chromosomes combine = genetic variety
Hoverflies mating in midair flight.
MEIOSIS • Prophase I: the chromosomes
condense and homologous chromosomes pair up to form tetrads.
• Metaphase I: the tetrads are all arranged at the metaphase plate.
• Anaphase I: the homologous chromosomes separate and are pulled toward opposite poles.
• Telophase I: movement of homologous chromosomes continues until there is a haploid set at each pole.
• Cytokinesis : by the same mechanisms as mitosis usually occurs simultaneously
• Prophase 2: spindle reforms and chromosomes move toward the metaphase plate.
• Metaphase 2: sister chromatids lined up on the
metaphase plate.• Anaphase 2: sister chromatids
are separated and pulled toward opposite poles of the cell.
• Telophase 2 and Cytokinesis: nuclei form at
either pole, and each cell is finally divided into two identical daughter cells.
MEIOSIS
Mitosis vs. Meiosis
REPRODUCTIONSEXUAL
• EXAMPLES: – Sexual Reproduction
• DNA from 2 individuals merge to form one.
• Animals, plants
– Fertilization• Pollen is delivered to female
part of plant.• Flowering plants
ASEXUAL• EXAMPLES:
– Fragmentation/Regeneration• Body of parent breaks and
produces offspring.• Fungi, moss, sea stars,
planarian
– Budding• Offspring grows out of parent.• Yeast, hydras
KNOWLEDGE CHECK
1. Label each of the following as either Asexual or Sexual reproduction:
• Spores budding• Nearly all organisms reproduce this way• Mitosis• Meiosis• Starfish is cut in half; both halves grow into a
whole starfish.• One parent needed• Not identical to parents• Two parents needed• Identical to parent• Sperm and eggs
KNOWLEDGE CHECK
ASEXUAL SEXUAL• Spores budding• Mitosis• Starfish is cut in half; both
halves grow into a whole starfish.
• Identical to parent• One parent needed
• Not identical to parents• Two parents needed• Sperm and eggs• Meiosis• Nearly all organisms
reproduce this way.
SHOULD WE MESS WITH MOTHER
NATURE?
MAKING IT JUST RIGHTSELECTIVE BREEDING
• The process of using specific plants or animals with specific traits to reproduce offspring with those traits
• These breeded plants/animals can be: – Larger in size– Provide more food– Resistant to disease
HYBRIDIZATION• The process of crossing to
plants/animals with different variations of the same trait
• The resulting offspring is created to have the best traits of the parents.
• Examples: – Corn: farmers each year try to
grow corn that are disease free and higher quality.
– Animals: if 2 different species are bred, a stronger but sterile species may be produced
MAKING IT JUST RIGHT
• Involves using two plants/animals that have the same or similar genes.
• The offspring produced will be purebred.• If purebreds are created, specific genes can be passed along.• Inbreeding, though, can cause a population to die.
– Since they are genetically similar, if one animal/plant comes down with a disease, the entire population may have it.
• INBREEDING
BREEDING EXAMPLES
Due to inbreeding, all cheetahs are closely related.
Miniature Horse was specifically bred small to work in mines.
Disease resistance, greater nutritional value
Mule combines the best traits of a horse and a donkey.
GENETIC ENGINEERING• Processes in which genes with specific DNA
strands are removed and transferred into another organism. – This process is much faster then altering organisms
through breeding techniques.
• Genetic engineering is used in biotechnology, medicine, and cloning.
GENETIC ENGINEERING
BIOTECHNOLOGY• Involves growing cells for
industrial purposes• Agriculture:
– Many plants and crops are susceptible to disease.
– Scientists have been able to isolate fighting genes and insert them into plants/crops for better survival rates.
GENETIC MODIFICATION• Genetic engineering produces
a lot of strong feelings among people.
• PROS: – Crops and farm animals may be
produced to better tolerate drought, disease, and infestations, therefore increasing the food production around the world.
• CONS: – Many people are concerned
about mixing genetic material with different species.
– Once in the wild, the effects of changes are out of the scientists hands.
GENETIC ENGINEERING
MEDICINES• Insulin has been able to be
created through Genetic engineering.– Insulin was once made from
animals, but people were allergic to it. Now it is created from bacteria with no allergies and is less expensive.
• Vaccines have been able to be produced through Genetic engineering.– Vaccines such as Hepatitis B are
now less expensive to produce and can be made in mass production.
CLONING• Clones are living things that
have exactly the same genes.
• Agriculture has done this forever: – Taking clippings of plants and
replanting them– The cuttings grow into new
and identical plants.
• Humans and animals, however, become more controversial:– Is it ok to clone spare body
parts?
GENETIC ENGINEERING
GENE THERAPY• Faulty genes inside a
human bodies can be replaced with normal, healthy ones
• Unfortunately, most cells in our body only live for a short period of time. – The new cells with the new
genes can function for a short period of time.
WHAT WOULD YOU DO?
• The more we know about DNA and genes, the more we may be able to predict our future.
• People today can be screened for certain genetic conditions.
• For example – If a person is found to be a
carrier of a specific gene defect, he/she will need to make a choice if he/she are to have kids.
– Perhaps you carry a gene for cancer which may or may not turn on. What would you do?
KNOWLEDGE CHECK
1. Name three types of breeding and a reason why they are used.
2. What is Genetic engineering?
3. Why is Genetic engineering supported by some yet forbidden by others?
KNOWLEDGE CHECK1. Name three types of breeding and a reason why they are
used. Selective breeding, hybridization, inbreeding. All 3 can be used to make specific higher yielding crops. Crops less vulnerable to disease and animals for specified jobs
2. What is Genetic engineering? Processes in which genes with specific DNA strands are removed and transferred into another organism.
3. Why is Genetic engineering supported by some yet forbidden by others? Supported = create medicines and cells for people to survive
Forbidden = Messing with mother nature. Do not have control if changes were to get into the wild