Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Site-specific recombinase technology wikipedia , lookup
Vectors in gene therapy wikipedia , lookup
Y chromosome wikipedia , lookup
Designer baby wikipedia , lookup
Polycomb Group Proteins and Cancer wikipedia , lookup
Microevolution wikipedia , lookup
X-inactivation wikipedia , lookup
GENES, ALLELES, AND CHROMOSOMES • All living things carry their genetic information in DNA • Sections of DNA with instructions for making proteins are called genes • DNA coils up to form structures called chromosomes • Chromosomes come in pairs, one from mom and one from dad REVIEW: WHAT DO WE KNOW ABOUT MITOSIS? 1. It makes more cells! 2. It begins with one cell, ends with two identical cells BIG BANG THEORY CLIP… https://www.youtube.com/watch?v=HV5kPiDYC3M But… • Why can’t Sheldon actually reproduce through mitosis? MITOSIS: • Essential for growth and repair of plant, animal, and human tissue. • Results in TWO daughter cells that are IDENTICAL HOMOLOGOUS CHROMOSOMES • Chromosomes that carry the same genes • One from mom and one from dad • Remember- genes are instructions for making proteins, and proteins determine traits ALLELES • So each of the homologous chromosomes has one copy of a gene from mom and one from dad • These copies are called alleles and may be the same or different versions • Green peas or yellow peas • Smooth seeds or wrinkled seeds • Tall plant or short plant KARYOTYPE • A photo of the chromosomes in a dividing cell that shows an individual’s chromosomes arranged by size. HUMAN KARYOTYPE SHOWING 23 PAIRS OF HOMOLOGOUS CHROMOSOMES KARYOTYPE CONT’D • Each of a human’s 46 chromosomes has thousands of genes, so the presence of all chromosomes is essential for normal functioning Humans who are missing a chromosome don’t survive past the embryo stage Humans with more than two copies of a chromosome may survive but will not develop properly (this is called trisomy). SO WHAT’S MEIOSIS??? MEIOSIS • We can’t use SOMATIC cells (body cells with homologous chromosomes) to reproduce sexually • We need special cells called GAMETES (sperm and egg) • Gametes only have ONE chromosome from each homologous pair • The process of separating homologous chromosomes and making gametes is called meiosis WHY MEIOSIS? • No meiosis = no sperm or eggs. • No sperm or eggs = no fertilization. • No fertilization = no sexual reproduction SPERM AND EGG CELLS ARE: • Reproductive Cells • Also called Gametes • Haploid (n)- only have half of the normal chromosome number • The normal number found in somatic cells is called diploid (2n) PHASES OF MEIOSIS • Meiosis occurs in two parts: •Meiosis I - homologous chromosomes are separated, the cell splits in 2 •Meiosis II - each sister chromatid is separated, both cells split in 2 for a total of 4 RESULT OF MEIOSIS: 4 HAPLOID DAUGHTER CELLS! FERTILIZATION: Human Sperm cell + Human Egg Cell = Fertilized Egg Zygote Embryo 23 chromosomes 23 chromosomes 46 chromosomes (haploid, n) (haploid, n) (diploid, 2n) MITOSIS MEIOSIS Makes somatic (body) cellsskin, blood, liver Makes gametes- Sperm & Egg Divide Once =2 Diploid Cells (2n) Divide Twice= 4 Haploid Cells (n) One division, four Phases: Two divisions, four phases each: Prophase Metaphase Anaphase Telophase/ cytokinesis Meiosis I Prophase I, Metaphase I, Anaphase I, Telophase I/ cytokinesis Meiosis II Prophase II, Metaphase II, Anaphase II, Telophase II/ cytokinesis CROSSING OVER • When homologous chromosomes pair up early in meiosis I, they can swap pieces (sections of DNA) • This results in a new combination of alleles and increases genetic diversity MITOSIS AND MEIOSIS SIMULATIONS http://sepuplhs.org/high/sgi/teachers/genetics_act3_si m.html Mitosis Meiosis Makes 2 daughter cells Makes somatic cells Both makes 4 daughter cells DNA replicates during interphase Makes gametes Daughter cells are identical to parent Daughter cells are diploid (2n) one round of division individual chromosomes line up during metaphase One parent cell divides Prophase Metaphase Anaphase Telophase Daughter cells are different Daughter cells are haploid (n) two rounds of division homologous pairs line up in metaphase I YOUTUBE VIDEO http://www.youtube.com/watch?v=zGVBAHAsjJM&safe=active