Chromosomes

Every organism has a set of coded instructions for a trait called genes. Heredity is the passing of these instructions from one generation to another. Chromosomes are what carry the genetic information, and they are composed of DNA. Heredity

Chromosomes in eukaryotes and prokaryotes are different single chromosome circular chromosome made only of DNA found in cytoplasm copies its chromosome and divides immediately afterwards many chromosomes linear chromosomes made of chromatin found in a nucleus copies chromosomes, then the cell grows, then goes through mitosis to organize chromosomes in two equal groups Chromosomes in eukaryotes and prokaryotes are different

Gregor Mendel, an Austrian monk of the nineteenth century, made the discoveries that is the foundation of our knowledge of genetics. Mendel

He did his experiments because he wondered why pea plants had different characteristics. Tall and short plants Green and yellow seeds Round (smooth) and wrinkled seeds Each different form o of a characteristic is called a trait. Mendel’s Experiments

A gene is a set of information that controls a trait A gene is a set of information that controls a trait. It is a segment of DNA that codes for a specific trait. Genes occur in at least two forms. These forms are called alleles. Alleles can be dominant or recessive. Genes

Alleles are the form of a gene found on a chromosome.

Dominant alleles hide or mask recessive alleles. An allele whose trait always shows up in the organism when the allele is present. Example: Purple flower color is controlled by a dominant allele An allele that is masked when a dominant allele is present. Example: White flower color is controlled by a recessive allele. Dominant alleles hide or mask recessive alleles.

Numbers of chromosomes Constant for each cell in the body (except sex cells which only have half sets). Constant throughout the life of an individual (you don’t lose or gain chromosomes) Constant for all members of a species Numbers of chromosomes

Mouse= 40 Maize=20

Humans have 46 chromosomes in every cell, except for the sex cells. Human sex cells have 23 chromosomes. Humans have 46 chromosomes in every cell, except for the sex cells.

Male Karyotype of Human Chromosomes Female Karyotype of Human Chromosomes Chromosomes are placed in pairs called homologous pairs based on the genes located on them.