Non-Mendelian Genetics

Eukaryotic organisms

Eukaryotic organisms

May have arisen 2.7 bya, but first fossils are 1.5 bya

• Nucleus with chromosomes

• Mitotic spindle

• Undergo meiosis for sexual reproduction

• Many have mitochondria or chloroplasts

Symbiotic relationship

One in which organisms, people, or things exist together in a way that benefits them all.

Mt and Cp fact

Mitochondria and chloroplasts are ancient descendants of ingested bacteria. This is why they have separate genomes!

Mitochondria

Organelles involved in cellular respiration, which converts biochemical energy from nutrients to ATP (energy).

ATP

Is a molecule of stored energy that can be used for several crucial cellular processes.

Oxidative phosphorylation

The electron transport chain system of the mitochondria transport ions to the intermembranal space, creating a gradient.

Substrate-level phosphorylation (Krebs Cycle)

Also makes ATP through a series of chemical reactions in the matrix of mitochondria

Mitochondrial genome (8 points)

• Circular

• Double-stranded

• Supercoiled DNA

• No histone proteins

• Linear mt genomes in PROTOZOA (often euks) and FUNGI

• Many mt per cell

• Genome in plants, animals, and fungi is similar in type of genes, but genome size varies. Humans about 20 kb, but some plants are 2 million

• In mammals

  • 13 for proteins

  • 22 for tRNA

  • One each for the small and large subunits of rRNA.

mt Genome Replication

• Semiconservative

• At any phase of the cell cycle

• Bases not equally distributed on both strands- HEAVY AND LIGHT STRANDS bc one strand will have too many purines, and other complementary pyrimidines.

• Ori opens “D Loop” region where H strand goes under synthesis first, followed by L strand

mt Genes

• Most proteins encoded by nuclear genes, but some on mt itself

• Ribosomal proteins coded by: Nuclear genes

• rRNA coded by mt

• Transcription is unusual bc a single RNA molecule is made, and cut into smaller pieces

• tRNAs cut out of the single transcript by specific enzymes: Freeing mRNA and rRNA

• No 5’ caps on mt mRNA, but a poly-A tail is added to the 3’ end as in nuclear mRNA

• No introns in animal mtDNA, but they are found in YEAST AND PLANTS

Translation in mt

• Start codons are close to the 5’ end, no leader sequences

• tRNA called fMet-tRNA is used to initiate protein synthesis- also unique mt initiation factors, elongation factors, and release factors

• Only PLANT MT USE UNIVERSAL GENETIC CODE OF NUCLEAR GENOME

  • Animal and fungal have a slightly dif. code for translation.

Genetic Relationships via mtDNA

• Used to trace human familial relationships

• Dif. mt genes are used to reconstruct the evolutionary history of many dif. organisms.

• Phylogenies are revolutionizing evolutionary biology.

Chloroplast genomes (9 points)

• Green algae and photosynthetic protists

• Double-stranded

• Circular

• No histone proteins

• Supercoiled

• Multiple copies in each nucleoid

• 80kb and 600kb

• Universal code in translation

• Gene org. similar to mtDNA: rRNA, tRNA’s, and some genes for photosynthesis, transcription, and translation, but many proteins come from nuclear DNA

Summary of mtDNA and cpDNA

• Both co-dependent with eukaryotic cells

  • mt make ATP, but require proteins made in cp to function

  • cp make ATP and sugars (light and dark reactions) during photosynthesis- like mt, they require proteins made in cytoplasm to exist

• mt uses modified genetic code. Cp uses standard

• mt are inherited maternally (most cases), cp maternally in flowers, other plants paternally.

Rules of Non-Mendelian Inheritance

1. Mendelian rations not found with extranuclear genes. Meiosis-based segregation does not occur

2. Reciprocal crosses in eukaryotes are not the same bc inheritance is based towards one sex and there is no meiosis based segregation.

3. Extranuclear genes can not be mapped to the chromosomes of the nucleus because they are not inherited the same way

4. Not affected by substituting a nucleus with a dif. genotype.

Uniparental Inheritance

Genes inherited through mtDNA or cpDNA are the same in all progeny as ONE of the parents, usually maternal inheritance bc mother’s cytoplasm in her gamete usually exceeds father’s sperm.

Male Mitochondria

Sperm get energy from: The “midpiece” section. Contains huge numbers of mt , it provides ATP for the tail, or flagellum.

Fertilization: Acrosome releases enzymes that allows one single winner

Nucleus contains genetic material needed to make the zygote- only head of sperm is drawn into the cytoplasm of the egg.

40 million- billion sperm is normal

Maternal Inheritance

• Mitochondrial inheritance

• Sometimes cytoplasmic DNA/RNA

• Mt in egg