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Chapter 8: Cell Reproduction Part 1: Overview
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Objectives Be able to explain the difficulties a cell faces as it increases in size Be able to compare and contrast sexual & asexual reproduction Be able to describe the structure of a chromosome Be able to identify the differences in structure between prokaryotic chromosomes and eukaryotic chromosomes Be able to explain the differences between sex chromosomes and autosomes
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Limits to Cell Size Nearly all cells grow by increasing in size At some point, they divide There are two main reasons cells divide rather than continue growing: – ____________________ The larger a cell becomes, the more demands the cell places on its DNA – ________________________ A larger cell is less efficient in moving nutrients and waste materials across the cell membrane
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Surface Area to Volume Ratio The size of a cell is limited by the relationship of the cell’s outer surface area to its volume, or its surface area–to–volume ratio As a cell grows, its volume increases much faster than its surface area does Why is this important to cells?
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Division of the Cell Before a cell becomes too large it divides into two “daughter” cells _________: is the process by which a cell divides into two new daughter cells
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Cell Division & Reproduction All organisms produce new organisms like themselves During reproduction, organisms transmit hereditary information
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Two Types of Reproduction Asexual Reproduction: produces new organisms that are exactly the same as the original organism – Examples: strawberries, amoebas, bacteria, starfish, onions etc. Sexual Reproduction: produces a genetically unique organism from the combining of the parents’ DNA – Examples: humans, tigers, some plants, whales, etc.
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Compare & Contrast Asexual ReproductionSexual Reproduction
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Facts about DNA It is a long, thin molecule that stores ________ ______________. It is made of nucleotides Nucleotides are made of a sugar, a phosphate, and a nitrogen base In human cells, its consists of approx. 3 billion nucleotides In eukaryotes, DNA is found in the _________. In prokaryotes, DNA is found in the ___________.
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Chromosomes Chromosomes are rod-shaped structures made of DNA & proteins The DNA & proteins are tightly coiled together The proteins that eukaryotic DNA wraps around are called __________ Histones help maintain the shape of a chromosome & keep it tightly packed
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Chromosome Structure of Eukaryotes
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Chromosome Structure Each chromosome consists of 2 identical halves called ___________ The 2 chromatids are held together by a ______________.
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Chromosome Structure Normally DNA is not so tightly coiled into chromosomes Chromosomes only appear right before cell division When cell division is not occurring, DNA is less tightly coiled as __________.
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Chromosome Number Every species has a characteristic number of chromosomes in each cell Human & animal chromosomes are categorized into 2 groups: ____________ & _______________.
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Sex Chromosomes & Autosomes Sex chromosomes: are the chromosomes that determine the sex of an organism – In humans, they are either X or Y – Females are _____ – Males are _____ Autosomes: are all the other chromosomes of an organism – Humans have 44 autosomes (22 pairs)
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Chromosome Numbers Every organism produced by sexual reproduction has 2 copies of each autosome One copy comes from _____ and the other comes from ______. The 2 copies of each autosome are called ______________________ – Meaning they are the same size, shape and carry the same traits
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Human Karyotype A karyotype is pictorial diagram showing all the chromosomes of an organism
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Chromosome Numbers: Diploid vs. Haploid Cells Diploid cells: have 2 sets of homologous chromosomes – All human cell except the sex cells are diploid – Abbreviated 2n – In humans, 2n = ____ or ____ pairs Haploid cells: have only 1 set of chromosomes – Sperm & egg cells are haploid – Abbreviated 1n – In humans, 1n = ____
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