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What is genetics?
the study of the inheritance, or the passing from parents to offspring, of traits
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When did Modern Genetics study start?
mid 1800's
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Who is the father of genetics?
Gregor Mendel
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What does Gregor Mendel study?
he studied genetics using pea plants
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Who was Gregor Mendel?
A catholic monk who studied genetics
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How did Gregor Mendel cross breed his pea plants? List the steps in order.
He cut off the pollen-containing structures from the short pea plant
He collected the tall plant pollen using a brush
He placed the tall plant pollen into the pistils of the short plant flowers.
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Review the plant chart from your text book for Mendel's experiments.
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What are the male gametes called?
sperm
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What are the female gametes called?
eggs
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What kind of cells are gametes?
Haploid cells
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How many chromosomes do haploid cells have?
23
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How many chromosomes do diploid cells have?
46
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How many chromosomes do human cells have?
Most human cells have 46 chromosomes. except for the gametes or human sex cells (gametes) which contain 23 chromosomes.
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Why do haploid cells only have 23 chromosomes?
Because they only have one copy of a chromosome pair.
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When two diploid gamete cells combine at fertilization what is formed?
a diploid zygote
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What type of reproduction combines two haploid cells to form a diploid zygote
sexual reproduction or meiosis
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In Mendel's theories what are his "factors" commonly known as today?
genes
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The traits in that Mendel was studying were controlled by what?
factors (known as genes today)
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How many genes do diploid organisms have for a specific trait?
They have two genes. One from each parent.
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What are the different forms of the gene for a trait called?
alleles
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What does it mean to be purebred for a particular trait?
It is when the organism's two alleles for a particular trait are the same.
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If an organism's two alleles are not coded the same for a particular trait then the organism is known as a?
hybrid
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In a hybrid organism what trait will be displayed in the organism?
The dominant trait
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The trait that is shown or displayed is called the?
phenotype
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Each allele in the set of two alleles for a trait is either __________________ or ____________.
recessive
dominant
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In a genotype what does an upper case letter represent?
it represents the dominant allele
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Ina genotype what does a lower case letter represent?
it represents the recessive allele
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In a hybrid genotype what phenotype would be displayed?
The phenotype that matches the dominant allele would be seen. The recessive allele would be masked.
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What is a phenotype?
It is an organism's physical appearance; the physical expression of an organism's genes
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What is a genotype?
It is a organism's genetic makeup
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MEMORIZE THE CHART OF DOMINANT/RECESSIVE TRAITS IN HUMANS.
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Genes are arranged on what?
chromosomes
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Where are chromosomes located?
in the nucleus
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Chromosomes occur in ___________.
pairs
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In sexual reproduction the haploid sperm and egg cells contribute how many chromosomes?
23; They contribute 1 member of each set of chromosomes.
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The diploid zygote has how many chromosomes?
two of each chromosome for a total of 46 (2 pairs of 23)
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What are punnett squares used for?
They are used to show genetic crosses
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What do the number of squares in a Punnet Square represent?
the individual squares represent the genetic possibilities of the offspring for two parents
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What is incomplete dominance?
It is a type of inheritance in which the alleles for a particular characteristic are neither dominant nor recessive, resulting in a “blending” of the two expressions of the gene. Ex. pink snapdragons
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What is codominance?
It is the expression of both alleles for a trait in an organism. Ex. roan cattle.
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Why does codominance occur?
Because both alleles are dominant and can not mask each other.
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What is polygenic inheritance?
It is an inheritance pattern in which two or more genes work together to produce a single trait.
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What is an example of polygenic inheritance?
human hair color.
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What is an example of codominance?
roan cattle
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What is an example of incomplete dominance?
snapdragon color
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What are multiple alleles?
It is an inheritance pattern in which there are more than two possible alleles for a singe trait
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What is an example of multiple alleles?
human blood type
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What are sex chromosomes?
They are the chromosomes that determine if an organism is male or female.
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What chromosomes are responsible for determining if humans are male or female?
The 23rd set of chromosomes
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What sex chromosomes do females have?
Females have two X chromosomes
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What sex chromosomes do males have?
They have 1 X and 1Y chromosomes.
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What chromosomes is larger; the X chromosome or the Y chromosome?
The Y chromosomes is smaller
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Do female eggs have an X chromosome or a Y chromosome on their 23rd chromosome?
They have the X chromosome
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Do male sperm have an X chromosome or a Y chromosome on their 23rd of chromosome?
They have a Y chromosome
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Which parent determines the sex or gender of the offspring?
The male sperm determines the gender of the offspring
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What are sex-linked traits?
It is a characteristic that is coded for by a gene on the X chromosome or the Y chromosome.
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What is an example of a sex-linked trait
color-blindness
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Are most sex-linked traits carried on the X chromosome or the Y chromosome?
Most are carried on the X chromosome, but there are some that are carried on the Y chromosome.
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Study the sex linked chart for color blindness on p. 124 in text
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