Biology (Genetics) - NCEA L1

A, C, T, G

bases of DNA

A+T, C+G

the base pairing rule

chromosomes

threadlike structures made of DNA molecules that contain the genes

DNA

A molecule containing the genetic information that makes up the chromosomes.

DNA shape

double helix

nucleotides

Basic units of DNA molecule, composed of a sugar, a phosphate, and one of 4 DNA bases

DNA replication

the semi-conservative process of the production of identical copies of DNA molecules.

Stage one of DNA replication

An enzyme unwinds the parent DNA strand by breaking the hydrogen bonds between bases.

Stage two of DNA replication

Enzymes bond the nucleotides together to form a new strand.

Stage three DNA replication

New nucleotides bond with the bases on the parent DNA molecule.

Stage 4 of DNA replication

At the end of the process, two molecules of DNA have been produced.

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.

Gene

A segment of DNA on a chromosome that codes for a specific trait

Genotype

An organism's genetic makeup, or allele combinations.

Phenotype

An organism's physical appearance, or visible traits.

Protein

A long chain of amino acids that are chemically bonded together.

amino acids

building blocks of proteins

Allele

Different forms of a gene

homozygous dominant

Both alleles (factors) for a trait are the same and dominant (AA)

homozygous recessive

Both alleles (factors) for a trait are the same and recessive (aa)

Heterozygous

An organism that has two different alleles for a trait

why are alleles in pairs

One allele is from your mother, one from your father.

homologous pair

a pair of chromosomes, one from each parent, that have relatively similar structures and gene values

Mitosis

cells are able to grow and then divide to form two 'daughter' cells

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.

Stage 2: Mitosis

The DNA condenses into large chromosomes that are visible under a light microscope. The nuclear membrane disappears.

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.

stage 4 of mitosis

The fibres pull the chromatids apart and they move to the ends of the cell.

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.

Stage 6 of Mitosis

The cell membrane and cytoplasm separates into two separate daughter cells.

Why is mitosis important?

Used for growth and the repair of damaged cells

Meiosis

Cell division that produces reproductive cells in sexually reproducing organisms

How many chromosomes are in the gametes?

23

gametes

reproductive or sex cells

Punnett Square

diagram showing the gene combinations that might result from a genetic cross

why might the probability be incorrect?

The Punnett square only shows the chances of what might occur each time an event is undertaken.

Karyotype

A picture of all the chromosomes in a cell arranged in pairs

How many pairs of chromosomes do humans have?

23 pairs

What alleles determine gender?

X and Y

Which alleles produce a male?

XY

Which alleles produce a female?

XX

Purebred

the offspring of many generations that have the same traits

Mendel's Peas

showed dominant vs. recessive genes. (a+a and A+A homozygous A+a heterozygous)

pedigree chart

A chart which shows several generations of related families and how traits are passed down through the offspring.

Pedigree Chart Symbol For Unaffected Female

Open Circle

Pedigree Chart Symbol For Affected Female

Closed Circle

Pedigree Chart Symbol For Unaffected Male

Open Square

Pedigree Chart Symbol For Affected Male

Closed Square

sexual reproduction

A reproductive process that involves two parents that combine their genetic material to produce a new organism, which differs from both parents

asexual reproduction

A reproductive process that involves only one parent and produces offspring that are identical to the parent.

Humans use which type of reproduction?

sexual reproduction

Variation

differences in physical traits of an individual from the group to which it belongs