Lecture #22 Honors Biology Ms. Day Haploid vs Diploid Lecture #22 Honors Biology Ms. Day

REVIEW: Draw and Label the Pieces of a Duplicated Chromosome chromatid Sister chromatids kinetochore Spindle fibers centromere Gene band (Duplicated) chromosome

Think: “t” for TWO chromatids and “d” for DUPLICATED

Different Types of Cells There are 2 types of cells in an organism Somatic cells: all body cells 2. Gametes: reproductive cells (sperm and egg)

Different cell types  different cell divisions Eukaryotic cell division consists of Mitosis = division of the nucleus Called karyokinesis Cytokinesis = division of cytoplasm Occurs in somatic cells In meiosis Gamete cells are produced after chromosome number is cut in ½

Chromosome Number Gametes (sperm/egg) have 1 copy of each chromosome called haploid (1n) Somatic (body) have 2 copies of each chromosomes called diploid (2n)

Haploid vs. Diploid Haploid= when a cell has 1 copy of each chromosome. Expressed as n = 23 Diploid= when a cell has 2 copy of each chromosome. (a.k.a TOTAL # of C’s in organisms) Expressed as 2n = 46 n Haploid sperm cell Haploid egg cell n Fertilization 2n Diploid Zygote cell

Pairs of Chromosomes Chromosomes have a “twin” (matching pair) Ex: Human somatic cells have 23 PAIRS of chromosomes (total 46 C’s) All pairs of chromosomes differ in size, shapes, and set of genes. Homologous Chromosomes = chromosomes that are similar in shape, size, and genes.

Homologous Chromosomes SIMILAR: 1. Size 2. Shape 3. Genes they carry DIFFERENT specific gene information (order of ATCG’s) B b

ZYGOTE = 1st diploid body cell of organism Set of Chromosomes Each chromosome set contain 2 “homologues” or “twins” Each homologue is also called an autosome A chromosome that does NOT determine gender Each homologue in a pair comes from each parent! Also have a “sex chromosome” pair Chromosomes that DO determine gender fertilization ZYGOTE = 1st diploid body cell of organism

Sex cell has MANY chromosomes including 1 sex chromosome Sex chromosomes vs. Sex cell (sperm/egg)…are NOT the same!!! X or Y= sex chromosome Sex cell has MANY chromosomes including 1 sex chromosome

Practice #1…How many chromosomes are present in…? Organism Clue Body Cell # Sex cell # Diploid # (2n) Haploid # (1n) a leaf cell of corn has 20 chromosomes an egg cell of a gorilla has 24 chromosomes a human liver cell has 46 chromosomes a gamete of a housefly has 6 chromosomes 20 10 20 10 48 24 48 24 46 23 46 23 6 12 12 6

Practice #2…How many chromosomes are present in…? What is the DIPLOID (2n) number of this organism? Hint: Count ALL the chromosomes!! 2n = 8 X X X X X X XX nucleus What is the HAPLOID (1n) number of this organism? n = 4

Practice #3…How many chromosomes are present in…? What is the DIPLOID (2n) number of this organism? 2n = 12 X X X X X X X X XX X X nucleus What is the HAPLOID (1n) number of this organism? 1n = 6

Chromosomes Determine Your Gender Humans have 23 pairs of chromosomes 22 pairs are autosomes (chromosomes that are NOT involved in making gender) Also called homologous chromosome pairs 1 pair are sex chromosomes (NOT HOMOLOGOUS; different genes) The sex chromosomes are “X” and “Y” “XX” is a girl “XY” is a boy X Egg cells ALWAYS have “X” chromosome Y X Y

an ordered, visual representation of ALL chromosomes in a human cell A karyotype an ordered, visual representation of ALL chromosomes in a human cell Arranged according to homologous pairs 5 µm Pair of homologous chromosomes Centromere Sister chromatids

Chromosomes are photographed during METPHASE (middle of mitosis)

Karyotypes (pictures of chromosomes) Used to study chromosomes & look for LARGE mutations (ex: chromosomal translocations, deletions, extra chromosomes) To make a karyotype 1. scientists take a picture of a cell’s chromosomes during metaphase and STAIN the chromosomes 2. Cut out the chromsomes and arranged them according to size and gene band pattern 3. They # the chromosome pairs **Use #1 through 23 4. #23 = ALWAYS sex chromosome pair (not homologous… NOT similar in genes it holds)

a REAL view…wow!!!