MCAS

1
MCAS 3 DNA and Heredity

• Everything about the nucleus in one afternoon

2
Todays topics

• Mitosis and the cell cycle
• DNA and protein synthesis
• Meiosis and genetics

3
Where is DNA?

• Chromatin- loosely wound DNA and proteins
• Located in nucleus of cells or nucleoid of
  bacteria
• Nucleolus- produces ribosomes

http//micro.magnet.fsu.edu/cells/nucleus/images/n
ucleusfigure1.jpg
4
Alternative arrangement

• Condenses to form chromosomes
• Tightly wound DNA and histones
• Livings things have different numbers of
  chromosomes
• Haploid- one set
• Diploid- two sets

http//home.planet.nl/gkorthof/korthof59.htm
5
Mitosis produces new identical cells

• Repair injuries
• Replace old cells
• Allow for growth
• One cell becomes 2- what about the DNA?

http//www.gussco.com/images/custom/wbBandaid-Fing
er.jpg
http//www.sciencemuseum.org.uk/on-line/lifecycle/
153.asp
http//www.yellow-springs.k12.oh.us/
6
What to do? The Cell cycle

• Duplicate the DNA you have (chromatid to
  chromosome)
• Split the two copies away from each other
• Daughter cells are still diploid

http//www.micro.utexas.edu/courses/levin/bio304/g
enetics/mitosis.gif
7
Mitosis division of the nucleus

• Centrioles- organize microtubules
• Spindle fibers- attach to chromosomes
• Aster- spindle fibers at either end
• BAT- ID stages!

http//library.thinkquest.org/C0123260/basic20kno
wledge/images/basic20knowledge/cell20division/mi
tosis.gif
8
Cell Cycle Checkpoints
Checkpoints make sure Cell is ready before
division If the cell proceeds without Meeting
the checkpoint Requirements CANCER
http//homepage.mac.com/enognog/cell20cycle.jpg
9
Cell divides through Cytokinesis

• Animals- pinch
• Plants- build cell plate

http//everyschool.org/u/logan/cellreproductionx/j
onesc/pictures/cytokinesis3.jpg
10
DNA up close

• Function- store hereditary material, direct
  production of proteins
• Polymer made of nucleotide monomers
• Sugar- deoxyribose
• Base- A,T,G,C,U
• Phosphate group

http//www.msu.edu/course/isb/202/ebertmay/drivers
/nucleotide.jpg
11
DNA double helix

• Alternating sugar- phosphate backbone
• BIG bases purines
• Adenine
• Guanine
• SMALL bases pyrimidines
• Cytosine
• Thymine
• Held together with hydrogen (weak) bonds

http//www.agen.ufl.edu/chyn/age2062/lect/lect_02
/3_36.gif
12
DNA replication- stores hereditary material

• Helicase unzips
• New nucleotides fit in with complimentary base
  pairing
• Enzymes link together (DNA polymerase)
• Proofreading for errors

13
DNA- codes the direction of proteins

• DNA passed through generations
• Proteins are responsible for traits

http//www.phschool.com/science/biology_place/bioc
oach/images/translation/centdogtl.gif
14
RNA

• BAT- compare and contrast!

http//www.daviddarling.info/images/RNA.gif
15
Transcription

• mRNA is complimentary to DNA
• Takes place in nucleus
• Product is mRNA
• RNA polymerase
• Cap and tail added

http//fig.cox.miami.edu/cmallery/150/gene/c7.17.
7b.transcription.jpg
16
Translation

• mRNA read by ribosome in cytoplasm
• Uses tRNAs to put in appropriate amino acid
• Product is polypeptide
• Ribosomes and tRNAs are key players

http//nobelprize.org/educational_games/medicine/d
na/a/translation/pics/translation2.gif
http//library.thinkquest.org/C004535/media/transl
ation.gif
17
How to make a protein

• Read DNA strand
• Use complimentary bases for mRNA
• Look for the start AUG (maybe)
• Break the mRNA into codons (groups of 3)
• Look up the codons in a table
• If given an anticodon table use that instead
• Read in 3s till the end

18
mRNA table
http//www.biology.lsu.edu/heydrjay/1201/Chapter17
/SCI_Amino_Acid_CIRCLE.jpg
19
Mutations!

• Point- CHANGE to one nucleotide- changes one
  amino acid
• Frameshift mutation- ADD/DELETE one nucleotide-
  changes all amino acids after it (changes reading
  frame of codons)

20
So far

• Pass DNA from cell to cell within an organism-
  Mitosis
• Use DNA within and organism to express traits-
  Protein synthesis
• Whats next- moving DNA from one generation to
  another

21
Methods of reproduction

• Asexual- pass on all of your genetic material-
  regular mitosis
• Sexual- combine genetic material with another
  person- only pass on half
• Solution MEIOSIS!

22
Function of Meiosis

• Produce haploid cells from diploid ones
• Produce sex cells like sperm and eggs

23
Stages of meiosis

• Two rounds of division
• Four total cells
• Homologs stay together during prophase 1
  crossing over

http//www.yorku.ca/kdenning/2140202006-7/meios
is.gif
http//www.phschool.com/science/biology_place/labb
ench/lab3/crossovr.html
24
Only pass on half of material Genetics

• Which of your two copies will you give to a sex
  cell?
• Which sex cell will end up with each sex cell?
• What will happen when two new copies end up in
  the same cell?

25
Separate chromosomes separate alleles

• Law of segregation
• Two alleles for same
• Trait separate
• Law of independent
• Assortment
• Each allele has a
• 50 chance to end
• Up in a gamete,
• Regardless of others

26
Genetics vocab

• Trait- observable characteristic
• Alleles- versions of a trait- dominant and
  recessive
• Phenotype- physical appearance
• Genotype- genetic makeup
• Homozygous- both alleles are same
• Heterozygous- two alleles are different

27
One trait cross

• Punnett Square
• Test crosses- mate
• With recessive
• Ratios- 31, 11
• Percentages

http//cache.eb.com/eb/image?id774rendTypeId4
28
Two trait cross
http//tosaweb.ncsd.k12.wy.us/faculty/lbell/Geneti
cs/Images/GB2520Gen20.jpg
29
Pedigrees for human traits

• Identify people by numbers, roman numerals
• Shaded have trait
• Squares males
• Dominant or recessive?
• Determine genotypes of individuals

http//www.ucl.ac.uk/ucbhjow/bmsi/rfexam_images/i
mg00007.gif
30
Non-Mendelian inheritance- modern genetics

• Incomplete- heterozygote has blend
• Red x white pink
• Codominance- heterozygote has both
• black x white speckled
• Multiple alleles- more than 2, each gets 2
• Blood types- A,B,O
• Polygenic- more than 2 spots, accumulate alleles
• Hair color, skin color
• Sex linked-trait on X chromosome-males have only
  1
• Color blindness, hemophilia, baldness

31
Chromosomal Inheritance

• Picture of chromosomes karyotype

Could reveal aneuploidy as a result Of
nondisjunction during meiosis Monosomy- only 1
copy Trisomy- 3 copies
http//anthro.palomar.edu/abnormal/abnormal_4.htm
http//www.uic.edu/classes/bios/bios100/lectf03am/
nondisjunction.jpg
32
Chromosomal mutations
http//staff.jccc.net/PDECELL/evolution/mutations/
chromrear1.gif
33
3 levels of DNA mutation

• Nucleotide seqence
• Regions of a chromosome
• Whole chromosomes missing/extra

34
Times that DNA can be mutated

• Inherited from parents- germ line
• DNA replication- affects all daughter cells
• Transcription/translation- affects that protein
  only