6.1 Meiosis Chapter 6 notes

General info __________________– requires two parents and produces offspring that are genetically different from each other

General info Sexual reproduction – requires two parents and produces offspring that are genetically different from each other

______________– variation, or inherited genetic differences, in a species

Genetic diversity – variation, or inherited genetic differences, in a species

Genetic diversity – variation, or inherited genetic differences, in a species In eukaryotic organisms, the chromosome number is referred to as the ______________(2n) since there are two sets of chromosomes

Genetic diversity – variation, or inherited genetic differences, in a species In eukaryotic organisms, the chromosome number is referred to as the diploid number (2n) since there are two sets of chromosomes

Genetic diversity – variation, or inherited genetic differences, in a species In eukaryotic organisms, the chromosome number is referred to as the diploid number (2n) since there are two sets of chromosomes Humans inherit one set of chromosomes, the ______ _______(1n), from each parent

In eukaryotic organisms, the chromosome number is referred to as the diploid number (2n) since there are two sets of chromosomes Humans inherit one set of chromosomes, the haploid number (1n), from each parent

More general info Haploid chromosomes are carried in gametes (sex cells), specialized cells necessary for reproduction  Male gametes are called _____ and female gametes are called _____ 

More general info Haploid chromosomes are carried in gametes (sex cells), specialized cells necessary for reproduction  Male gametes are called sperm and female gametes are called eggs 

During fertilization, an egg cell joins a sperm cell and the genetic information is combined, resulting in a diploid cell called a ______  The zygote undergoes mitosis and cell division and develops into an embryo

During fertilization, an egg cell joins a sperm cell and the genetic information is combined, resulting in a diploid cell called a zygote  The zygote undergoes mitosis and cell division and develops into an embryo

Stages of meiosis Process that produces four gametes with half the number of chromosomes

Meiosis I Prophase I – homologous chromosomes pair up (one from each parent) and non sister chromatids exchange genetic material (called crossing over) 

Metaphase I – homologous chromosomes pair up at the equator

Anaphase I – homologous chromosomes separate and are pulled to opposite poles by the spindle fibres

Telophase I – one chromosomes from each homologous pair is at each pole of the cell

Interkinesis – 2 cells result and each cell grows and makes proteins but unlike mitosis, DNA does not replicate

Meiosis II Prophase II – there is one chromosome of the homologous pair in each cell

Metaphase II – the X-shaped chromosomes form a single line across the middle of the cell

Anaphase II – sister chromatids move to opposite poles of the cell (each one is now considered a chromosome)

Telophase II – spindle fibres begin to disappear and a nuclear membrane forms around each set of chromosomes

Cytokinesis – the two daughter cells are separated

Crossing over In crossing over, parts of non-sister chromatids exchange segments of DNA to create an infinite amount of genetic variation 

Independent assortment is when homologous pairs of chromosomes separate at the equator and move towards opposite ends... you never know which one will go which way 

In sperm cell, all four cells may develop into mature sperm but in egg cell there is an unequal division of cytoplasm and organelles so three cells disintegrate and only one large egg cell remains

Chromosome mutation During meiosis, pieces of chromosomes can be lost, duplicated or moved within a chromosome or moved to another chromosome Mutations occur when cells are exposed to mutagens  Large chromosome errors are usually prevented from being passed along because the offspring will die before birth or fail to reach reproductive age 

A karyotype is a picture of all our chromosomes arranged in a particular order

Karyotypes are studied to help physicians diagnose and treat patients with genetic disorders (syndromes) like Down syndrome