Life Science Chapter 6
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What is genetics?
the study of the inheritance, or the passing from parents to oﬀspring, of traits
When did Modern Genetics study start?
Who is the father of genetics?
What does Gregor Mendel study?
he studied genetics using pea plants
Who was Gregor Mendel?
A catholic monk who studied genetics
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.
Review the plant chart from your text book for Mendel's experiments.
What are the male gametes called?
What are the female gametes called?
What kind of cells are gametes?
How many chromosomes do haploid cells have?
How many chromosomes do diploid cells have?
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.
Why do haploid cells only have 23 chromosomes?
Because they only have one copy of a chromosome pair.
When two diploid gamete cells combine at fertilization what is formed?
a diploid zygote
What type of reproduction combines two haploid cells to form a diploid zygote
sexual reproduction or meiosis
In Mendel's theories what are his "factors" commonly known as today?
The traits in that Mendel was studying were controlled by what?
factors (known as genes today)
How many genes do diploid organisms have for a specific trait?
They have two genes. One from each parent.
What are the different forms of the gene for a trait called?
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.
If an organism's two alleles are not coded the same for a particular trait then the organism is known as a?
In a hybrid organism what trait will be displayed in the organism?
The dominant trait
The trait that is shown or displayed is called the?
Each allele in the set of two alleles for a trait is either __________________ or ____________.
In a genotype what does an upper case letter represent?
it represents the dominant allele
Ina genotype what does a lower case letter represent?
it represents the recessive allele
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.
What is a phenotype?
It is an organism's physical appearance; the physical expression of an organism's genes
What is a genotype?
It is a organism's genetic makeup
MEMORIZE THE CHART OF DOMINANT/RECESSIVE TRAITS IN HUMANS.
Genes are arranged on what?
Where are chromosomes located?
in the nucleus
Chromosomes occur in ___________.
In sexual reproduction the haploid sperm and egg cells contribute how many chromosomes?
23; They contribute 1 member of each set of chromosomes.
The diploid zygote has how many chromosomes?
two of each chromosome for a total of 46 (2 pairs of 23)
What are punnett squares used for?
They are used to show genetic crosses
What do the number of squares in a Punnet Square represent?
the individual squares represent the genetic possibilities of the offspring for two parents
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
What is codominance?
It is the expression of both alleles for a trait in an organism. Ex. roan cattle.
Why does codominance occur?
Because both alleles are dominant and can not mask each other.
What is polygenic inheritance?
It is an inheritance pattern in which two or more genes work together to produce a single trait.
What is an example of polygenic inheritance?
human hair color.
What is an example of codominance?
What is an example of incomplete dominance?
What are multiple alleles?
It is an inheritance pattern in which there are more than two possible alleles for a singe trait
What is an example of multiple alleles?
human blood type
What are sex chromosomes?
They are the chromosomes that determine if an organism is male or female.
What chromosomes are responsible for determining if humans are male or female?
The 23rd set of chromosomes
What sex chromosomes do females have?
Females have two X chromosomes
What sex chromosomes do males have?
They have 1 X and 1Y chromosomes.
What chromosomes is larger; the X chromosome or the Y chromosome?
The Y chromosomes is smaller
Do female eggs have an X chromosome or a Y chromosome on their 23rd chromosome?
They have the X chromosome
Do male sperm have an X chromosome or a Y chromosome on their 23rd of chromosome?
They have a Y chromosome
Which parent determines the sex or gender of the offspring?
The male sperm determines the gender of the offspring
What are sex-linked traits?
It is a characteristic that is coded for by a gene on the X chromosome or the Y chromosome.
What is an example of a sex-linked trait
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.
Study the sex linked chart for color blindness on p. 124 in text
Life Science Chapter 6
BJU Life Science Chapter 6