Rewind your Mind and Meiosis Creating Gamete Cells

REWIND YOUR MIND………………..MITOSIS Mitosis is division of the nucleus. This process occurs in 4 phases: PROPHASE METAPHASE ANAPHASE TELOPHASE The final stage is called Cytokinesis which is division of the cytoplasm. This results in the formation of 2 genetically identical daughter cells. Mitosis takes place in somatic (body) cells. These cells are said to be diploid because they contain twice the number of Chromosomes or 2n.

First let’s Rewind Your Mind……. DNA is made of millions of nucleotides in the shape of a double helix! Adenine pairs with Thymine Cytosine pairs with Guanine The sequence of the nitrogen bases makes all living things unique. When DNA makes a copy of itself, it is called DNA Replication

DeoxyriboNucleic RiboNucleic NEVER CAN 21 Adenine, Thymine, Cytosine, Guanine Adenine, Uracil, Cytosine, Guanine DeoxyriboseRibose

TRANSCRIPTION  TRANSLATION  PROTEIN SYNTHESIS: Label the picture below Transcription Translation Protein or Amino Acid Chain Transcription is when the mRNA copies the protein code from the DNA. This takes place in the nucleus. DNA reads: TAC CAT GGG GAT ACT mRNA copies: AUG GUA CCC CUA UGA Translation is when the tRNA reads the mRNA codons and brings the appropriate amino acids to the ribosome to create an amino acid chain (protein or polypeptide) mRNA reads: AUG GUA CCC CUA UGA Translated to Amino acids: Met – Val – Pro – Leu - STOP

What is a mutation? A change/mistake in the genetic material (DNA) of an organism. What can cause mutations? Environmental factors such as UV rays, pollution even viruses. What are 2 types of mutations? Gene and Chromosomal What are the 2 types of Gene Mutations? Point and Frameshift

Point Mutation : when one base pair is substitued by another. For example: normal DNA reads: TAC CAT GGG CAC AAT ACT Mutated DNA reads: AGG GUA CCG GUG UUA UGA This can cause a silent mutation which means a change in a base pair into another that codes for the same amino acid. This can also cause a missense mutation which means point mutation that still codes for an amino acid, just the wrong amino acid. Or it can cause a nonsense mutation which means it prematurely codes for stop codon resulting in a nonfunctional protein.

Deletion insertion A frameshift mutation caused by a deletion of base-pairs or insertions of extra base pairs will result in a frameshift in the reading of the DNA. This mistake ends up causing a missense or a nonsense mutation For Example:

MEIOSIS: a process by which the number of homologous chromosomes per cell is reduced by half the number and is referred to as haploid cells (n).

Meiosis only happens in Gametes ( sex cells – egg or sperm)

MITOSIS vs MEIOSIS 2 4 Identical Different Somatic (body) Gamete (Sex) Skin, Liver, Heart… Sperm & Egg Once Twice animals, plants, and fungi All organisms

What are homologous chromosomes? a similar pair of chromosomes, one from the father & one from the mother

What is a Diploid Cell? A cell that contains 2 complete sets of homologous chromosomes is said to be diploid or 2n Somatic (body cells) are diploid cells. Blood cells Brain cells Nerve cells Liver cells

What is a Haploid Cell? A cell that contains 1 complete set of chromosomes. These are called gametes or sex cells (egg or sperm)

Meiosis: production of gametes Alternating stages –chromosome number must be reduced diploid  haploid 2n  n –humans: 46  23 meiosis reduces chromosome number makes gametes –fertilization restores chromosome number haploid  diploid n  2n haploid diploid

Meiosis I and Meiosis II resulting in 4 haploid daughter cells with “n” number of chromosomes There are 2 distinct divisions of meiosis: Interphase I Prophase I Metaphase I Anaphase I Telophase I Metaphase II Telephase II and Cytokinesis

Each chromosome pairs with its corresponding homologous chromosome to form a structure called a tetrad. There are 4 chromatids in a tetrad. Meiosis I - Prophase I

Overview of meiosis I.P.M.A.T.P.M.A.T interphase 1prophase 1metaphase 1anaphase 1 telophase 1 prophase 2 metaphase 2anaphase 2telophase 2 2n = 4 n = 2

As homologous chromosomes pair up, they exchange genetic information in a process called crossing over producing new combinations of alleles – accounting for variation among species.

Sexual Reproduction Creates Genetic Variability Sexual reproduction allows us to maintain both genetic similarity & differences. Baldwin brothers Jonas Brothers Martin (dad) Charlie Sheen Emilio Estevez Wayan Brothers Jackson Brothers

Gamete (sex cell) Formation in Meiosis 2n n n nn Sperm - male Egg- female Polar Bodies 2n n Human Sperm + Human Egg Human Zygote = 46 N+ N = 2N

2n n n nn MITOSIS vsMEIOSIS

KARYOTYPE: A photograph of all the chromosomes inside a somatic (body) cell placed from largest to smallest with sex chromosomes at the end.