Anthropology Mini Essays
Lecture 4: Cell Biology and Protein Synthesis
Key Questions
• What are the types of cells that make up human bodies?
• What is the most important function of a gene (of DNA)?
• What are the steps of protein synthesis?
• What are the two types of cell division?
• What is the evolutionary significance of meiosis?
The Cell
Eukaryotic Cells
• Structurally complex cells composed of carbohydrates, lipids (fats), nucleic acids, proteins. – First appeared 1.2 billion years ago
• Somatic cells—cells of the body and body tissues; skeletal cells, muscle cells, neurons, blood cells; all cells in the body are somatic cells except for the gametes
• Gametes—sex cells; sperm are the male sex cell and are produced in the testes; ova are the fema
Chromosomes
Chromosomes • Humans have 46 (23
homologous pairs)
• Diploid chromosomes—the full complement of chromosomes in a somatic cell
• Haploid chromosomes— half the complement of chromosomes, one member of each pairsex cells
Structures composed of a DNA molecule and associated proteins
Chromosomes
• Autosomes— chromosomes that carry the genetic information for all physical characteristics EXCEPT sex (44 of the 46 chromosomes in humans)
Structures composed of a DNA molecule and associated proteins
Chromosomes
• Autosomes— chromosomes that carry the genetic information for all physical characteristics EXCEPT sex (44 of the 46 chromosomes in humans)
• Sex chromosomes
– X and Y
– XX for female
– XY for male
Structures composed of a DNA molecule and associated proteins
DNA and Chromosomes
1 trillion somatic cells
46 chromosomes per cell
100-1000 genes per chromosome
DNA is coiled
around specialized
proteins that give it structure
a specific sequence of nucleotide base pairs make a gene
1 trillion somatic cells
46 chromosomes per cell
100-1000 genes per chromosome
DNA is coiled
around specialized
proteins that give it structure
a specific sequence of nucleotide base pairs make a gene
DNA Structure
Proteins
http://trc.ucdavis.edu/biosci10v/bis10v/week2/2webimages/0143.gif http://www.irondisorders.org/News/SickleCell.jpg
Proteins
• The primary function of DNA is protein synthesis
• Proteins:
– Chains of amino acids
– Built from DNA/genes
– Amino acid order is determined by gene
– Amino acid order is crucial to protein function
http://image.slidesharecdn.com/proteinsandaminoacids-140714080054- phpapp02/95/proteins-and-amino-acids-32-638.jpg?cb=1405326023
Protein Synthesis
RiboNucleic Acid
• Similar to DNA structure
• Various types/functions
• Single stranded
• Uracil replaces thymine
• Facilitates protein synthesis
– turns genes into functions
Transcription
• Messenger RNA (mRNA) • Copies order of bases • Takes code out of nucleus
Translation Transfer RNA (tRNA)
“Reads” mRNA’s message
Strings amino acids together
Constructs proteins
Protein Synthesis
• https://youtu.be/I_c8GlWRQJohttps://youtu.be/I_c8GlWRQJo
Sickle-Cell Anemia
https://www.fi.edu/sites/default/files/styles/featured_large/public/General_EduRes_Heart_RedBloodCel ls.jpg?itok=mTMuH5xK
Sickle-Cell Anemia
• Disease that affects shape of hemoglobin—molecule that carries oxygen in blood – Abnormal hemoglobin can clog blood vessels—causes
major life-threatening problems
• Hemoglobin is a protein, which is produced by protein synthesis based on the information in a gene – Abnormal cells result from a mutation in the DNA
sequence that codes for hemoglobin—a different allele, or version of the hemoglobin gene
– Mutation—minor alteration in the sequence of bases in a DNA strand
• This tiny alteration makes major changes in the protein that interrupt its normal function and cause disease
Sickle Cell Anemia
From: Campbell NA, Reece JB. 2002. Biology, 6th Ed. San Francisco: Benjamin Cummings. SCA mutant hemoglobin results from change in ONE amino acid (out of 146 in the whole hemoglobin chain)
Sickle-Cell Anemia
• There are 146 amino acids in the chain for hemoglobin.
– Sickling hemoglobin is caused by a change in just one nucleotide base in the gene for hemoglobin, leading to a change in just one amino acid.
Sickle-Cell Anemia
Cell Division
J. BRILL et al., Curr. Biol. 15, 1401–1406 and 1407–1412 (2005)
Cell Division
• Mitosis—cell division in somatic cells; cells make identical copies of themselves
– Start with 1 diploid cell, end with 2 identical diploid cells
• Meiosis—cell division in gametes
– Start with 1 diploid cell, end with 4 distinct haploid cells
DNA Replication
Mitosis
1 2
6 5 4
3
1. DNA replicates (4 copies of each chromosome, 2 pair homologous chromosomes
2. Nuclear membrane disappears
3. Chromosomes align at center of cell
4. Separate into pairs 5. Move to opposite sides of
cell (2 copies of each chromosome to each side)
6. Cell membrane pinches, creates 2 new diploid cells
Mitosis
• http://www.youtube.com/watch?v=cvlpmmvB _m4http://www.youtube.com/watch?v=cvlpmmvB_m4http://www.youtube.com/watch?v=cvlpmmvB_m4http://www.youtube.com/watch?v=cvlpmmvB_m4
Meiosis
Essentially the same as mitosis EXCEPT Recombination occurs
Meiosis
Exchange of genetic material between homologous chromosomes. Mixes it up even more than sexual reproduction would alone—some genes from the maternal and paternal chromosomes trade places.
Meiosis
An extra division of chromosome pairs produces FOUR HAPLOID daughter cells
Meiosis
• http://www.youtube.com/watch?v=4B071d9Y wbc&feature=plcphttp://www.youtube.com/watch?v=4B071d9Ywbc&feature=plcphttp://www.youtube.com/watch?v=4B071d9Ywbc&feature=plcphttp://www.youtube.com/watch?v=4B071d9Ywbc&feature=plcp
Mitosis vs. Meiosis
Errors in Meiosis
Significance of Meiosis
• For Evolution:
– Increases variation
• Variation is one of the Necessary and Sufficient Conditions for Natural Selection
• Raw material on which selection acts
• Errors:
– Copying errors = wrong proteins produced
– Nondisjuction = trisomy (21, sex chromosomes)
– Sometimes, errors turn out to be beneficial
