Module 2 Review

1. Module 2 Review

2. The main stages of the cell cycle are: Gap 1, Synthesis, Gap 2, & Mitosis. • Gap 1 (G1): cell growth and normal functions, copy organelles (most cells spend most of their time here) • Only proceed to S if the cell has enough nutrition, adequate size, undamaged DNA • Synthesis (S): copies DNA • Gap 2 (G2): additional growth • Mitosis (M): includes division of the cell nucleus (mitosis) and division of the cell cytoplasm (cytokinesis) • Mitosis occurs only if the cell is large enough and the DNA undamaged.

4. Cell size is limited. • Cell volume increases faster than surface area. • Cells need to stay small to allow diffusion and osmosis to work efficiently.

5. Chromosomes condense at the start of mitosis. • Chromosomes: carry genetic information (DNA) that is passed from one generation of cells to the next. • DNA wraps around proteins (histones) that condense it.

6. DNA plus proteins (histones) is called chromatin. • Each chromosome is composed of two chromatids • Sister chromatids are held together at the centromere. • Telomeresprotect DNA and do not include genes(like the caps on shoelaces)

7. Mitosis and cytokinesis produce two genetically identical daughter cells. • Interphase prepares the cell to divide. • DNA is duplicated.

8. Mitosis divides the cell’s nucleus in four phases - PMAT • Prophase – first & longest • Chromosomes condense, spindle fibers form, and the nuclear membrane disappears.

9. Mitosis divides the cell’s nucleus in four phases. • Metaphase • Chromosomes line up across the middle of the cell.

10. Mitosis divides the cell’s nucleus in four phases. • Anaphase • Sister chromatids are pulled apart to opposite sides of the cell.

11. Mitosis divides the cell’s nucleus in four phases. • Telophase • Two nuclei form at opposite ends of the cell, the nuclear membranes reform, and the chromosomes uncoil back into chromatin

12. Cytokinesis differs in animal and plant cells. • Cytokinesis is when the cytoplasm separates • Animal cells: membrane pinches the two new cells apart • Plant cells: a cell plate (new cell wall) separates the two new cells

13. Cell division is uncontrolled in cancer. • Cancer cells form disorganized clumps called tumors. • Benign tumors remain clustered and can be removed. • Malignant tumors metastasize, or break away, and can form more tumors.

14. Cancer cells do not carry out normal cell functions(this is part of why they’re so bad!) • Cancer cells come from normal cells with damage to genes involved in cell-cycle regulation. • Carcinogens are substances known to cause cancer (they damage those genes) • Chemicals, tobacco smoke, X-rays, UV rays, HPV • Cancer can also be caused by genetics (i.e. BRCA1) • Standard cancer treatments typically kill both cancerous and normal, healthy cells.

15. Apoptosis is programmed cell death. • Apoptosis is the process of programmed cell death. • Normal feature in healthy organisms

16. Binary fission is similar to mitosis. • Asexual reproduction is the creation of offspring from a single parent. • Pros: more efficient in favorable environments. • Cons: All respond to environment identically • Binary fission produces two daughter cells genetically identical to the parent cells. • Binary fission occurs in prokaryotes. • Some eukaryotic cells also reproduce asexually via mitosis – budding, fragmentation, vegetative reproduction

17. Multicellular organisms depend on interactions among different cell types. • Tissues are groups of cells that perform a similar function. • Organs are groups of tissues that perform a specific or related function. • Organ systems are groups of organs that carry out similar functions.

18. Specialized cells perform specific functions. • Cells develop into their mature forms through the process of cell differentiation. • Cells differ because different combinations of genes are expressed.

19. You have somatic cells and gametes. • Somatic Cells: • Are body cells • Make up all cells in body except foregg and sperm cells • DNA not passed on to children • Gametes: • Are egg or sperm cells • DNA passed on to children

20. Your cells have autosomes and sex chromosomes. • Human somatic cells have 23 pairs of chromosomes (46 total) • (1) Autosomes: pairs 1 – 22; carry genes not related to the sex of an organism • (3) Sex chromosomes: pair 23; determines the sex of an animal; control the development of sexual characteristics • (2) Homologous chromosomes: pair of chromosomes; one from each parent; carry the same genes but may have a different form of the gene (example: one gene for brown eyes and one gene for blue eyes)

21. Somatic cells are diploid; gametes are haploid. • Diploid (2n) • Has two copies of each chromosome (1 from mother & 1 from father) • 44 autosomes, 2 sex chromosomes • Somatic cells are diploid • Produced by mitosis • Haploid (1n) • Has one copy of each chromosome • 22 autosomes, 1 sex chromosome • Gametes are haploid • Produced by meiosis

23. Meiosis makes different haploid cells from diploid cells, reduces chromosome number & increases genetic diversity.

24. Homologous chromosomes (sometimes called homologues) • Pair of chromosomes • Inherit one from each parent • Carry same genes but code for different traits (different versions of the gene) • Separate during Meiosis I • Sister chromatids • Duplicates of each other • Each half of a duplicated chromosome • Attached together at the centromere • Separate in Meiosis II

25. Meiosis I • Occurs after DNA has been replicated (copied) • Divides homologous chromosomes in four phases.

26. Meiosis II • Divides sister chromatids in four phases. • DNA is not replicated between Meiosis I and Meiosis II. • Ends in 4 genetically different cells

27. Mitosis Vs. Meiosis Mitosis Meiosis Two cell divisions Homologous chromosomes pair up (Metaphase I) Results in haploid cells Daughter cells are unique • One cell division • Homologous chromosomes do not pair up • Results in diploid cells • Daughter cells are identical to parent cell

28. Haploid cells develop into mature gametes. • Gametogenesis is the production of gametes. • Gametogenesis differs between males and females. • Sperm (spermatogenesis) • Become streamlined and motile (able to move) • Primary contribution to embryo is DNA only • Egg (oogenesis) • Contribute DNA, cytoplasm, and organelles to the embryo • During meiosis, the egg gets most of the contents, the other 3 cells become polar bodies

30. Sexual reproduction creates unique combinations of genes. • Fertilization • Random • Increases unique combinations of genes • Independent assortment of chromosomes • Homologous chromosomes line up randomly along the cell equator • Increases the number of unique combinations of genes

31. Sexual reproduction creates unique combinations of genes. • Crossing over • Exchange of chromosome segments between homologous chromosomes • Increases genetic diversity • Occurs during Prophase I of Meiosis I • Results in new combinations of genes (chromosomes have a combination of genes from each parent)

32. Genetic linkage • Chromosomes contain many genes. • The farther apart two genes are located on a chromosome, the more likely they are to be separated by crossing over • Genetic linkage: genes located close to each other on the same chromosome tend to be inherited together

33. The same gene can have many versions. • A gene is a piece of DNA that directs a cell to make a certain protein. • Each gene has a locus, aspecific position on a pair ofhomologous chromosomes.

34. Each parent donates one allele for every gene. • Homozygous describes two alleles that are the same at a specific locus. Ex: (RR or rr) • Heterozygous describes two alleles that are different at a specific locus.Ex: (Rr) • An allele is any alternative form of a gene occurring at a specific locus on a chromosome. (gene=pea shape, alleles= wrinkled or smooth) • A dominant allele is expressed as a phenotype (visible trait) when at least one allele is dominant. • A recessive allele is expressed as a phenotype (visible trait) only when two copies are present.

35. Practice: Ff x ff • What words would you use to describe the P generation (parents)? • What would the phenotype and genotype be of the F1 generation? Phenotype: 50% Purple, 50% White Genotype: 50% Heterozygous, 50% Homozygous Recessive

36. purple white • Mendel drew three important conclusions. • 1. Traits are inherited as discrete units. • 2. Organisms inherit two copies of each gene, one from each parent. • 3. The two copies segregateduring gamete formation. • The last two conclusions arecalled the law of segregation.

37. Incomplete Dominance = BLENDING in heterozygotes • Neither allele is dominant over the other, so individuals with a heterozygous genotype show a blended phenotype somewhere in the middle. (i.e. red + white=pink) • Use different letters to represent each possible allele (instead of Rr use RW since there is not dominant or recessive allele) • Examples: feather color in chickens, flower color such as roses or snapdragons.

38. Phenotype ratio: 100% Pink Genotype ratio: 100% heterozygous

39. Co-dominance = TOGETHER or SPOTTED – both traits are FULLY and SEPARATELY expressed • Co means together, and BOTH alleles are dominant so they show up together. Ex: hair color in humans, fur color in cattle. • Use different letters to represent each possible allele (instead of Bb use BW since there is not dominant or recessive alleles)

40. B W B W Phenotype: 25% Black, 25% white, 50% black and white Genotype: 25% homozygous black, 25% homozygous white, 50% Hetero

41. Sex-Linked Inheritance • Some disorders are carried on the X chromosome. Examples of these disorders are color blindness, and hemophilia. • Only females can be carriers (heterozygous) because they have two X chromosomes • Maleseither have the allele (and hence show the trait) or they don’t. Males only get 1 X, so whatever they inherit on that 1 X is what you see.

42. Phenotype: 50% Normal vision females25% Normal vision males 25% Color Blind males Genotype: 25% XBXb (Carrier) 25% XbY 25% XBXB 25% XBY

43. Human Blood Types: Use both co-dominance and regular dominant/recessive. • A and B are co-dominant. O is recessive. • Use the chart to help with crosses.

44. phosphate group nitrogen-containing base deoxyribose (sugar) DNA is composed of four types of nucleotides. *DNA is a double helix DNA is made up of a long chain of nucleotides. Each nucleotide has three parts. • a phosphate group • a deoxyribose sugar • a nitrogen-containing base

45. G C A T Nucleotides always pair in the same way. • The base-pairing rules show how nucleotides always pair up in DNA. • A pairs with T • C pairs with G

46. new strand original strand Two molecules of DNA DNA REPLICATION - Two new molecules of DNA are formed, each with an original strand and a newly formed strand. Occurs in the NUCLEUS • DNA replication is semi-conservative, meaning one original strand and one new strand.

47. replication transcription translation • DNA contains the instructions to make proteins. RNA is a link between DNA and proteins.

48. RNA differs from DNA in three major ways. • DNA has a deoxyribose sugar, RNA has a ribose sugar. • RNA has uracil instead of thymine (found in DNA) • A pairs with U • DNA is a double stranded molecule, RNA is single-stranded.

49. Transcription makes three types of RNA. • Transcription copies a piece of DNA (a gene) to make a strand of RNA.

50. Transcription copies a piece of DNA to make RNA • Transcription makes three types of RNA. • Messenger RNA (mRNA) carries the message that will be translated to form a protein. • Ribosomal RNA (rRNA) forms part of ribosomes where proteins are made. • Transfer RNA (tRNA) brings amino acids (protein building blocks) from the cytoplasm to a ribosome to build the protein.