sci10 task 1

DNA Structure

Is a double helix, resembling a twisted ladder with two strands held together.

Backbone

Sides of a ladder, alternating sugar and phosphate groups.

Rungs

Formed by pairs of nitrogenous bases; adenine, thymine, cytosine, guanine.

Nucleotides

Building blocks of DNA. Consisting of sugar, phosphate group and nitrogenous base.

Phosphate Group

Attached to sugar, forming the backbone.

DNA Replication

1. The strands of the double helix separate from one another, exposing the bases. Within the nucleus are nucleotides that aren’t apart of the chain.

2. The nucleotides pair up with the exposed bases following the rules. The sugar and phosphate bond with neighbouring nucleotides and new strands of DNA are formed.

3. Resulting in two identical DNA molecules, each one a double helix. Identical to the original parent DNA.

4. The cell is now ready to divide.

Mitosis Purpose

Divides the nucleus, involved in growth and repair.

Mitosis Stages

Prophase I, Metaphase I, Anaphase I, Telophase I

Prophase

Centrioles move to the opposite ends of the cell, spindle forms and chromosomes become visible. Nuclear membrane breaks down.

Metaphase

The chromatid pairs line upon the equator of the spindle.

Anaphase

Chromatids separate at the centromere. They are pulled towards opposite ends of the cell.

Telophase

Nuclear membranes form. Spindle fibres disappear and chromosomes uncoil. Cytoplasm goes inwards so that a new cell membrane is formed. Creates two identical daughter cells.

Mitosis Result

Produces two identical daughter cells, with the same chromosome number.

Meiosis Purpose

Cell division process when chromosomes are halved to 23 to create gametes.

Meiosis Stages

Prophase I, Metaphase I, Anaphase I, Telophase I, Prophase II, Metaphase II, Anaphase II, Telophase II

Prophase II

In each of the daughter cells, a new spindle forms, the nuclear envelope breaks down, condensing into chromosomes again

Metaphase II

Chromosomes line up individually along the metaphase plate.

Anaphase II

Sister chromatids separate and are pulled towards opposite poles of the cell.

Telophase II

Nuclear membranes form around each set of chromosomes and they condense. Cytokinesis splits chromosomes into new cells.

Meiosis Produces

Each diploid cell undergoes two rounds of division to produce four haploid daughter cells.

Chromosomes

When your body makes new cells, DNA bunches itself into chromosomes. Rod-like structures seen in cells undergoing division. 46, 23 pairs. One from each parent.

Genes

A gene is a part of DNA that contains instructions that codes for a particular trait. It is inherited, can be passed onwards.

Alleles

Matching genes, one from each parent. Whilst they may be identical, they often have slight differences.

Haploid

A cell that contains a single set of chromosomes.

Diploid

A cell that contains two sets of chromosomes.

Sex Linked Inheritence

Refers to the traits determined by genes in sex chromosomes, leading to the different inheritance patterns.

Dominant Gene

Masks the expression of the recessive allele for the trait to be expressed. Is more likely to be inherited.

Recessive Gene

An allele whose effect is masked by a dominant allele, meaning a trait is only expressed with the inheritance of two copies of the recessive allele.

Punnet Squares

Helps to predict the variations that can come from cross-breeding.

Genotype

A person’s unique sequence of DNA.

Phenotype

Observable characteristics in an individual based on the expression of their genes.

Homozygous

Having two identical alleles of a particular gene or genes.

Heterozygous

Having different alleles for a particular trait.

Pedigrees

Usually depict inheritance patterns of genes and diseases.