1. Meiosis Review

2. Meiosis Sexual Reproduction
Separates homologous chromosomes, then sister chromatids
Results in haploid cells
Haploid=n
Diploid=2n
Homologous chromosomes: Chromosomes that pair up during meiosis. A person gets two chromosomes- one from their mom and one from their dad. The homologous chromosomes hold the same genes, but they probably have different alleles. The two purple and two pink chromosomes in this picture represents two pairs of homologous chromosomes.
Sister chromatids: Each chromosome is made of two identical sister chromatids, connected at the middle by a centromere. Each of the black and white cells have one chromatid in them.

3. Meiosis
The process of meiosis. In the first part of meiosis, homologous chromosomes separate. In the second part of meiosis, the sister chromatids separate. Here, the homologous chromosomes are not paired up by color like in the previous slide. Each homologous chromosome pair has one blue and one yellow chromosome.

4. Crossing Over
Segments of homologous chromosomes are broken off and switched during meiosis
Genetic variety is caused by two things. The first is due to the fact that a baby is made from two different gamete. The second is due to crossing over. In this process, some genes will switch from one homologous chromosome to the other, providing variety.

5.
Go here to watch an animation of meiosis.

6. Electrophoresis Fragments of DNA are loaded into the gel
Fragments travel down the gel and stop based on molecular size
DNA is a polar molecule, meaning it has a partially positively charged end and a partial negatively charged end. An electric charge is pulsed through the gel, and DNA fragments are attracted across the gel like a magnet. The smaller fragments move the farthest in the gel, so the bands at the bottom of the screen represent the smallest DNA fragments.

7. DNA

8. DNA Double helix shape Nucleotides/Base Pairs Adenine Thymine Guanine
Cytosine
The nucleotides are what holds all of the genetic material in DNA. Adenine (A) always binds with Thymine (T), and vise versa. Guanine (G) always binds with Cytosine (C), and vice versa.

9. RNA Similar to DNA Single-Stranded Four nucleotides: Adenine Uracil
Guanine
Cytosine
Although DNA and RNA hold the same genetic information, there are two major differences to remember between DNA and RNA. RNA is single-stranded while DNA is double-stranded. RNA does not contain Thymine (T) like DNA does, and instead has Uracil (U). A and U both have molecular structures, so they both bind with A.
RNA’s nucleotides bind in the following way: A-U and G-C

10. DNA  RNA  Protein
The Central Dogma of Biology is that DNA uses RNA to create proteins.

11. Proteins? Antibodies Enzymes Messengers Structural Components
Transport
Storage
Proteins make up nearly everything in our bodies- not just muscles!

12. This is a ball-and-stick model of a protein
This is a ball-and-stick model of a protein. A protein is made up of a LOT of amino acids, and the molecule folds on itself several times. Note that a protein is huge compared to a single nucleotide.

13. DNA  RNA DNA: ACG TTC GAA TTG RNA: UGC AAG CUU AAC
This is an example of how RNA would make a complementary strand based on a DNA strand.

14. Amino Acids Coded for in DNA, by three nucleotides
Each three nucleotides is one codon. Each codon codes for one amino acid. Notice that more than one codon codes for the same amino acid. For example, GUU and GUC would both code for Valine (Val).
A mutation in a DNA or RNA sequence means that one nucleotide changes. Using the same example, if GUU mutates to GUC, no phenotypic change would be made, since both code for Valine. However, if GUU mutates to GCU, there would be a phenotypic change, since the amino acid coded for would change from Valine to Alanine (Ala).

15. DNA Replication

16. DNA Replication consists of three major steps and each one uses one enzyme. The steps are as follows:
Helicase unwinds the DNA
DNA Polymerase adds complementary nucleotides down the half-DNA strand.
DNA Ligase binds the DNA strand together, finishing the process.
DNA can only be added in one direction- from the 5’ end to the 3’ end (not something you need to memorize, but this is helpful for the explanation). In the top strand, the nucleotides can be added in a smooth process as the helicase unwinds the DNA. In the bottom strand, this is not the case. The nucleotides have to be added in the direction away from where helicase is unwinding the DNA. This means that the nucleotides have to be added in small chunks, or fragments, called Okazaki fragments.

17. Protein Synthesis

18. rRNA
Protein synthesis happens in two steps: transcription and translation.
Transcription: a strand of mRNA (messenger RNA) is made with nucleotides that are complimentary to one of the DNA strands.
The mRNA leaves the DNA and the nucleus, and binds to a ribosome.
Translation: The rRNA (ribosomal RNA) attaches to the start codon. The tRNA (transfer RNA) recognizes the codon and the amino acid that it codes for, and attaches to the codon. This process is repeated at the next codon, and each amino acid is bound to the next one. The string of amino acids is extended until the tRNA reaches the stop codon, and the sequence of amino acids folds on itself and makes a protein.