lecture 6 Flashcards
How do plants grow?
Plant cells start small they exchange materials with the environment and they grow through the interphase and start mitosis.
How do plant cells divide into two?
Cell plate forms which is an accumulation of vesicles and divides the cell into two. This is for the plant cells.
How does the sexual life cycle work?
In a human life cycle, zygote is a single cell which is a fertilized egg. We went from one cell to billions of cells today. Getting from zygot to billion of cells is a zygot. Each of us produce sperms and eggs which collectively are referred to as gametes. When the cells combine together the process of fertilization begins.
What is haploid?
One complete set of genes. A haploid organism has one complete set of chromosomes. The number of chromosomes found in a haploid cell is different for each species. The number of chromosomes is designated by the letter n.
What are diploid?
Having two complete set of genes or two complete sets of chromosomes. The number of chromosomes varies a lot and it is not related to the size of the organism.
What type of organisms are diploid?
Humans are diploid organisms.
What does being diploid mean?
Being diploid means we have homologous pairs. A diploid human cell has 23 homologous pairs.
What does being haploid mean?
Haploid there is only 1 chromosomes from each homologous pair.
What are examples of haploid organisms?
Gametes are always haploid. Human sperm has 23 chromosomes 1 from each homologous pair same for the egg.
When are zygots diploid?
The zygot is diploid when it fuses the egg and the sperm. For each homologous pair one came from the egg and one from the sperm.
What type of division do gametes use?
The gametes use a specialized cell division called meiosis. This only occurs in t he production of gametes.
When does Meiosis start?
starts with they cell that started with the interphase.
meiosis process
Meiosis has two cell divisions.
The process of cell division does not
change the number of chromosomes therefore in order to produce gametes we need a process that turns diploid cells into haploid cells
o This process is called meiosis
Metaphase of meiosis I:
Homologous pairs of chromosomes lining up at the metaphase plate. The 4 chromosomes are still together. The spindles continue to pull and we get to anaphase.
Anaphase I
Homologous pairs split, chromosomes are pulled to opposite ends. This is the transition from being diploid to being haploid. The cell elongates at this point. Only two chromosomes being sent to opposite sides of the cells. Some bits of DNA are being mixed between chromosomes in each homologous pair.
Telophase I
New nucleus being formed in each end. The nuclear envelop assembles, the spindle breaks up, Each nuclei has two chromosomes one from each homologous pair. Cytokinesis begins. Each of the two cells is genetically unique.
Cytokinesis I
There’s a cleavage furrow. The plasma membrane pinches cytoplasm in two. After this Meiosis I is complete. There is no interphase here. Just a brief pause and no growing happening here. Then Meiosis II starts here.
What is meiosis II identical to?
Meiosis II is identical to mitosis.
What happens during crossing over? and when does it happen?
When homologous chromosomes come together to form tetrads, the arms of the chromatids can swap at random, creating many more possibilities for genetic variation of the gametes.
What do we start with and what is created during meiosis?
Start with 1 diploid cells Then we end up with 4 haploid cells. The haploid cells mature into gametes.
Matching pairs from mom and dad is a homologous pairs.
Meiosis and sexual life cycles
It start with zygote, then cell cycle, then multicellular organism, few specialized cells that go through meiosis.
Meiosis produces haploid cells that then becomes gametes. The gametes meet other gametes and fuse together in fertilization and form a zygote. That is a typical animal cycle.
Typical fungal life cycle
It starts with the zygote that goes right into meiosis. Goes from one diploid to 4 haploid. The haploid are not gamete, they are spores. If they land somewhere good they go through a cell cycle. The haploid cell goes through a cell cycle producing a multi cellular organism that is haploid. It continues through the cell cycle and produce gametes and can fuse together into fertilization to form a zygote.
Typical plants and algae cycle
Start with the zygote. It goes into the plant life cycle. It becomes a diploid multicellular organism. Then it goes through meiosis and it produces spores not gametes. Those spores go through the cell cycle going through a cell cycle that are haploid. It can produce gametes. Those gametes go through fertilization and fuse together and form another zygote.
Character or trait
A potentially variable quality or quantity in an organism.
Eg. flower colors, blood type, pea texture.
True breeding variety
When an organism has new generation and always have the same traits in each generation.
Hybrid
The offspring of two different varieties.
Monohybrid cross
Studying the inheritance of a single character in a hybridization experiment.
P: parental generation: It is the starting point for the experiment.
F1: First Filial generation: The offspring of the P generation.
F2: Second filial generation: Offspring of the F1 generation
explain the purple flower example
The parental generation was crossed (two true breeding variety)
F1 there were only purple flowers (one purple particle and one white particle)
F2 Then only one white and rest purple (the purple particles are dominant)
Particles of inherintance
One particle makes the petals grow purple and one would be white. Each pea plant inherited two such particles. The dominant particle determines the color of the flower even when the other type of particle is there.
Punnet square
The different combinations to be predicted in the next generation. For the second generation chance plays a bigger role in the genetic makeup of that generation.
Gene
A sequence of genetic material (DNA).
Locus
The place on a chromosome where a gene is located.
Allele
One form of a gene found at a particular locus.
Diploid
Having two alleles at each locus.
Haploid
One allele at each locus.
