Sexual and Asexual Reproduction Cell Reproduction TEST Friday, 11/13
How many chromosomes do humans have? What are Chromosomes? How many chromosomes came from your mom? How many chromosomes came from your dad?
What are Chromosomes? Chromosome a DNAcontaining structure that carries genetic information from one generation to the next. Chromosomes are inherited from parent cells. Every species has a specific chromosome number.
What are Chromosomes? Autosomes chromosomes with genes that do not determine an individual s gender How many autosomes do humans have? 44
What are Chromosomes? Sex Chromosomes chromosomes with genes that determine an individual s gender Humans X and Y X chromosome contains many vital genes unrelated to gender How many sex chromosomes do humans have? 2
What are Chromosomes? XY XX
Homologous Chromosomes Homologous chromosomes chromosomes that are the SAME size and have the SAME genes. Genes sections of DNA that code for proteins.
Haploid vs. Diploid Haploid describes cells containing half the number of chromosomes Which cells in our bodies are haploid? gametes What is the haploid number for humans? 23
Haploid vs. Diploid Diploid describes cells containing 2 of each chromosome Which cells in our bodies are diploid? Somatic cells What is the diploid number for humans? 46
Asexual Reproduction When a cell reproduces by asexual reproduction, One parent cell provides all the genetic information. 2 daughter cells are produced
Asexual Reproduction Daughter cells are genetically identical to the original parent cell and to each other. No genetic variation exists unless mutations occur. Genetic variation differences in the DNA Mutations changes in the DNA
When does the cell copy its DNA? S-phase (interphase) Why does the cell copy its DNA? To make identical copies for each daughter cell Sometimes, there are mistakes mutations We ll talk about these more later
Asexual Reproduction Builds the bodies of multicellular organisms. Somatic cells regular body cells Created by asexual reproduction (mitosis) Every cell in your body has the exact same DNA. Cells function differently based on which genes are turned on/off.
Some organisms reproduce by asexual reproduction to build populations. Examples: Prokaryotes binary fission Eukaryotes mitosis Asexual Reproduction
Asexual Reproduction ~ Advantages Does not require a mate. Saves time and energy. Occurs quickly. Populations grow rapidly. More offspring can be produced over time.
Asexual Reproduction ~ Disadvantages No genetic variation among offspring. Populations are only successful in environments with little stress. Nutrient availability, space, etc. No competition which limits adaptations to the environment.
Sexual Reproduction Requires TWO parent cells Each parent cell contributes half the genetic information for the offspring. Gametes haploid reproductive cells (sperm and egg) Formed by meiosis in the reproductive organs
Sexual Reproduction Zygote the diploid cell that results from the fertilization of the egg by the sperm
Sexual Reproduction ~ Advantages Produces genetically unique offspring. Competition among individuals produces a more successful or better adapted population. Genetic variation allows some organisms to survive when others cannot.
Sexual Reproduction ~ Disadvantages Requires TWO parent cells, so organisms must find a mate. Takes time and energy Slower process Slower population growth
Sources of Genetic Variation Crossing over occurs when homologous chromosomes swap genetic information at the beginning of meiosis (Prophase I)
Sources of Genetic Variation Law of Independent Assortment the random distribution of homologous chromosomes during meiosis (Metaphase I)
Sources of Genetic Variation Law of Independent Assortment influences the combination of genes in the gametes
Sources of Genetic Variation Random Fertilization Only 1 sperm can fertilize each egg.
Just Remember