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| The main sources of variation are usually from genetic recombination and mutation. Recombination is the result of the two sets of chromosomes that come together during fertilization. |
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| Egg and Sperm (sex cells) are produced by a process called meiosis. These sex cells or gametes carry one-half the number of chromosomes as other cells and are called haploid. The egg and sperm join during fertilization to form a diploid zygote, which grows by mitotic cell division to an adult. |
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| Chromosomes consist of genetic material called DNA. A gene is a specific sequence of DNA that controls the expression of a trait. The alternative forms of a gene are called alleles; that is, one allele is received from each parent for a given trait. |
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Gametes differ from the other cells of the body known as from somatic cells. Gametes are haploid (n) and somatic cells are diploid (2n). Gametes are formed by meiosis, a type of cell division that is actually two divisions resulting in four haploid daughter cells. Haploid gametes join to form a diploid zygote, thus keeping the chromosome number constant through each generation. Meiosis also increases genetic variability by generating new genetic combinations in offspring.
Each human can produce at least 6.4 million different gametes. Using the same calculation that was used in the table on page 17 of the text, the different genetic combinations in the offspring that can be produced by the mating of two individuals is 70 trillion. This newly formed zygote contains 22 pairs of autosomes and 2 sex chromosomes. |
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Genes code for a specific protein. Changes in DNA are called mutation. Mutations can be passed to the offspring when it occurs in the gametes or sex cells (sperm or egg).
Human somatic cells contain 46 chromosomes that consist of 2 sets of 23 pairs of homologous, or similar, chromosomes. One set is carried in the gamete received from each parent. Of the 23 pairs of chromosomes, 22 pairs are autosomal and 1 pair determines sex. |
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| Explain how we are biologically unique. |
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| Know z = p x m ... be able to explain the concepts behind this equation. each human can produce 6.4 mil. different gametes, genetic combination included 70 trillion possibilities. |
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| Differentiate between identical twins and fraternal twins |
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| identical twins are derived from the same fertilized egg. during the first cell division the egg can split, they are genetically identical. fraternal twins - 2 eggs are released during ovulation. |
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| Explain how recombination plays a role in variation |
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| use the ball in a bag theory and be able to explain meiosis |
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| Explain what a mutation is and how it occurs |
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| mutation can result from many different causes, including radiation, chemicals and UV light. know the example of Cystic Fibrosis |
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| Compare and contrast the types of reproduction: Mitosis and Meiosis |
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mitosis - when a cell replicates itself.
meiosis - chromosomal recombination occurs
look up more |
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| What is the difference between asexual and sexual reproduction |
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sexual - two mates
asexual - one organism
find more info |
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| Why do organisms engage in sexual reproduction even though it is not necessary to create new organisms |
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| genetic diversity ... allows the species to continue and evolve |
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| purpose and role of chromosomes within the cell |
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| long strands of DNA molecules. gamete diversity is derived from the distribution of maternal and paternal chromosomes |
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| What is the advantage of having two sets of chromosomes? |
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| increases the possible genetic combinations |
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| Autosomes and Sex Chromosomes |
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| autosomes - 22 sets of regular chromosomes. sex chromosomes - gametes, one sex of chromosomes |
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| Explain the difference between gametes and somatic cells |
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somatic - body cells
gametes - sex cells |
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| The phenotype of an individual organism is either its total physical appearance and constitution or a specific manifestation of a trait, such as size, eye color, or behavior that varies between individuals |
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| is the specific genetic makeup (the specific genome) of an individual, in the form of DNA. It is basically the type of gene. Together with the environmental variation that influences the individual, it codes for the phenotype of that individual. |
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| dominant trait refers to a genetic feature that hides the recessive trait. A dominant trait causes a phenotype that is seen in a heterozygous genotype. Many traits are determined by pairs of complementary genes, each inherited from a single parent. Often when these are paired and compared, one gene (the dominant) will be found to effectively shut out the instructions from the other, recessive gene. For example, if a person has one gene for blue eyes and one for brown, that person will always have brown eyes because they are the dominant trait. For a person to have blue eyes, both their genes must be blue (recessive). When a person has two dominant alleles, they are referred to as homozygous dominant. If they have one dominant allele and one recessive allele, they are referred to as heterozygous. |
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Recessive:
Homozygote:
Heterozygote: |
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| all talked about in dominant |
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| is the process through which a DNA sequence is enzymatically copied by an RNA polymerase to produce a complementary RNA. Or, in other words, the transfer of genetic information from DNA into RNA |
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| is the second process of protein biosynthesis (part of the overall process of gene expression).Translation occurs in the cytoplasm where the ribosomes are located. Ribosomes are made of a small and large subunit which surrounds the mRNA. In translation, messenger RNA (mRNA) is decoded to produce a specific polypeptide according to the rules specified by the genetic code. This is the process that converts an mRNA sequence into a chain of amino acids that form a protein. Translation is necessarily preceded by transcription. Translation proceeds in four phases: activation, initiation, elongation and termination (all describing the growth of the amino acid chain, or polypeptide that is the product of translation). |
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| is a single large macromolecule of DNA, and constitutes a physically organized form of DNA in a cell. It is a very long, continuous piece of DNA (a single DNA molecule), which contains many genes, regulatory elements and other intervening nucleotide sequences. A broader definition of "chromosome" also includes the DNA-bound proteins which serve to package and manage the DNA. |
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| are changes to the base pair sequence of genetic material (either DNA or RNA). Mutations can be caused by copying errors in the genetic material during cell division and by exposure to ultraviolet or ionizing radiation, chemical mutagens, or viruses, or can occur deliberately under cellular control during processes such as meiosis or hypermutation. |
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| (2n) cells have two copies (homologs) of each chromosome, usually one from the mother and one from the father. The exact number of chromosomes may be one or two different from the 2n number yet the cell may still be classified as diploid (although with aneuploidy). Nearly all mammals are diploid organisms, although all individuals have some small fraction of cells that display polyploidy. |
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| The haploid number is the number of chromosomes in a gamete of an individual. This is distinct from the monoploid number which is the number of unique chromosomes in a single complete set. |
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| Somatic cells, by definition, are not germline cells. In mammals, germline cells are the sperm and ova (also known as "gametes") which fuse during fertilization to produce a cell called a zygote, from which the entire mammalian embryo develops. Every other cell type in the mammalian body—apart from the sperm and ova, the cells from which they are made (gametocytes) and undifferentiated stem cells—is a somatic cell: internal organs, skin, bones, blood, and connective tissue are all made up of somatic cells. |
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| is a specialized germ cell that fuses with another gamete during fertilization (conception) in organisms that reproduce sexually. In species which produce two morphologically distinct types of gametes, and in which each individual produces only one type, a female is any individual which produces the larger type of gamete—called an ovum (or egg)—and a male produces the smaller type—called a spermatozoon (or sperm cell). |
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| is the process by which a cell separates its duplicated genome into two identical halves. It is generally followed immediately by cytokinesis which divides the cytoplasm and cell membrane. This results in two identical daughter cells with a roughly equal distribution of organelles and other cellular components. |
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| is the process that allows one diploid cell to divide in a special way to generate haploid cells in eukaryotes. |
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