10.1 Chromosomes Why are some cells smaller than others?

They have recently divided and have not grown to full size.

What allow these cells to become specialized into lung or muscle tissue?

Genes on chromosomes within each cell contain the instructions for building those

specialized tissues. How does each cell receive its genes?

Mitosis. chromosomes are copied, divided and received by daughter cells.

Developing embryo video

Karyotype

Male

Female

Down’s Syndrome

Formation of new cells

2 trillion cells are produced by adults each day.

Cell division – cells grow and develop depending on what they are dividing for: Healing wound Asexual reproduction

Gametes – organisms’ reproductive cells, such sperm and eggs.

DNA – must be present in each resulting cell. Stores information on what proteins to

make and when.

Prokaryote cell reproduction

Binary fission – is a form of asexual reproduction that produces identical offspring.

Process DNA is copied Add new cell membrane between the two DNA. Cell constricts Cell wall forms around cell membrane cell divides into two cells

Binary fission

Binary fission

Eukaryote cell reproduction

Gene – segment of DNA that codes for a protein or RNA molecule.

Chromosome – the DNA and proteins associated with DNA.

Chromatide – two exact copies of DNA that make up each chromosome.

Centromere – the point two chromatids are attached together.

Humans

23 pairs of different chromosomes 46 chromosomes

Differ in size, shape and genes.

Homologous chromosomes – are chromosomes that are similar in size, shape and genetic content.

All cells are somatic cells, except gametes. Diploid – two sets of chromosomes. Haploid – one set of chromosomes. N = one set of chromosomes. Humans

Haploid n=23 Diploid 2n=46

Zygote – is a fertilized egg cell, the first cell of a new individual.

Do not copy

Sex chromosomes

Autosomes – chromosomes that are not directly involved in determining the sex (gender) of an individual. Humans 22 pairs

Sex chromosomes – contains the genes that will determine the sex of the individual. Humans 1 pair (23)

Different sex traits (do not copy) Many plants and some animals (earthworms

and hydra) have both male and female sex organs in the same individual and produce both male and female gametes (sperm and egg, respectively).

Among some dioecious taxa (some species of fish, alligators and sea turtles) sex is determined by the environment, not genetics. Local concentrations of hormones or differences in temperature will cause the developing embryo to develop as either a male or a female.

Change in chromosome number It is essential to have all 46 chromosomes for

normal development and function. Trisomy – three copies of a particular

chromosome Trisomy 21 (Down’s syndrome) – extra copy of

chromosome 21.

Karyotype – a photo of the chromosomes in a dividing cell that shows the chromosomes arranged by size.

karyotype

Change in chromosome structure

Mutations – change in chromosomes’ structure. Breakage of chromosome

1.Deletion mutation – a piece of the chromosome breaks off completely.

2.Duplication mutation – a chromosome fragment attaches to its homologous chromosome.

3. Inversion mutation – chromosome piece reattaches to the original chromosome, but in reverse orientation.

4. Translocation mutation – a piece reattaches to nonhomologous chromosome.