threadlike structures made of DNA molecules that contain the genes
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DNA
A molecule containing the genetic information that makes up the chromosomes.
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DNA shape
double helix
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nucleotides
Basic units of DNA molecule, composed of a sugar, a phosphate, and one of 4 DNA bases
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DNA replication
the semi-conservative process of the production of identical copies of DNA molecules.
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Stage one of DNA replication
An enzyme unwinds the parent DNA strand by breaking the hydrogen bonds between bases.
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Stage two of DNA replication
Enzymes bond the nucleotides together to form a new strand.
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Stage three DNA replication
New nucleotides bond with the bases on the parent DNA molecule.
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Stage 4 of DNA replication
At the end of the process, two molecules of DNA have been produced.
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Why is the new strand identical to the old strand that was separated?
Complimentary base pairing ensures the correct nucleotide goes in the right place.
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Gene
A segment of DNA on a chromosome that codes for a specific trait
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Genotype
An organism's genetic makeup, or allele combinations.
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Phenotype
An organism's physical appearance, or visible traits.
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Protein
A long chain of amino acids that are chemically bonded together.
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amino acids
building blocks of proteins
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Allele
Different forms of a gene
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homozygous dominant
Both alleles (factors) for a trait are the same and dominant (AA)
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homozygous recessive
Both alleles (factors) for a trait are the same and recessive (aa)
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Heterozygous
An organism that has two different alleles for a trait
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why are alleles in pairs
One allele is from your mother, one from your father.
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homologous pair
a pair of chromosomes, one from each parent, that have relatively similar structures and gene values
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Mitosis
cells are able to grow and then divide to form two 'daughter' cells
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Stage one of mitosis
Before mitosis begins the chromosomes are not visible. Also invisible is the process of replication of the cell's DNA. Two copies will be required for each of the two daughter cells.
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Stage 2: Mitosis
The DNA condenses into large chromosomes that are visible under a light microscope. The nuclear membrane disappears.
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Stage three of mitosis
The chromosomes line up in random order in the middle of the cell. Fibres stretch across the cell to pull the chromatids apart.
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stage 4 of mitosis
The fibres pull the chromatids apart and they move to the ends of the cell.
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Stage 5 of Mitosis
The fibres disappear and a nucleus reforms. The chromosomes begin to uncoil and disappear from view. The center of the cell contracts, beginning the process of forming two separate cells.
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Stage 6 of Mitosis
The cell membrane and cytoplasm separates into two separate daughter cells.
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Why is mitosis important?
Used for growth and the repair of damaged cells
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Meiosis
Cell division that produces reproductive cells in sexually reproducing organisms
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How many chromosomes are in the gametes?
23
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gametes
reproductive or sex cells
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Punnett Square
diagram showing the gene combinations that might result from a genetic cross
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why might the probability be incorrect?
The Punnett square only shows the chances of what might occur each time an event is undertaken.
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Karyotype
A picture of all the chromosomes in a cell arranged in pairs
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How many pairs of chromosomes do humans have?
23 pairs
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What alleles determine gender?
X and Y
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Which alleles produce a male?
XY
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Which alleles produce a female?
XX
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Purebred
the offspring of many generations that have the same traits
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Mendel's Peas
showed dominant vs. recessive genes. (a+a and A+A homozygous A+a heterozygous)
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pedigree chart
A chart which shows several generations of related families and how traits are passed down through the offspring.
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Pedigree Chart Symbol For Unaffected Female
Open Circle
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Pedigree Chart Symbol For Affected Female
Closed Circle
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Pedigree Chart Symbol For Unaffected Male
Open Square
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Pedigree Chart Symbol For Affected Male
Closed Square
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sexual reproduction
A reproductive process that involves two parents that combine their genetic material to produce a new organism, which differs from both parents
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asexual reproduction
A reproductive process that involves only one parent and produces offspring that are identical to the parent.
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Humans use which type of reproduction?
sexual reproduction
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Variation
differences in physical traits of an individual from the group to which it belongs
Studied by 243 people
