VCE biology Units one and two: Unit two - Cell cycle, asexual and sexual reproduction, meiosis, cell growth and differentiation

Sherlock Holmes
Flashcards by Sherlock Holmes, updated more than 1 year ago
Sherlock Holmes
Created by Sherlock Holmes about 4 years ago


References: Jacaranda Nature of Biology VCE Units one and two, fifth edition, by Judith Kinnear and Marjory Martin.

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Question Answer
What are the stages of cell division and what happens in each stage? 1. Interphase - contains G1, S and G2 phase 2. Prophase - chromosomes pair up 3. Metaphase - chromosomes move to the middle 4. Anaphase - chromosomes move apart to poles 5. tTelophase - two new cells are made 6. Cytokinesis - cytoplasm divides.
What happens in each stage of Interphase? G1 - the cell grows before DNA replication S - DNA replication G2- cell prepares for division
What is mitosis? Nuclear division in somatic (normal body cells) and results in the production of two cells that are genetically identical to the parent. consists of only one cycle of cell division.
What is meiosis? Nuclear division of sex cells. Results in the production of Gametes (haploid cells) that carry half the genetic information as the parent. Consists of two cycles of cell division.
Why does meiosis contain two cycle of cell division? The first division separates the homologous chromosomes and the second division separates the chromatids.
What is Binary fission and how does it occur? a type of asexual reproduction where a cell divides into two cells, each having the potential to grow as big as the original cell. It begins with the replication of the genetic material followed by chromosome segregation and then cytokinesis.
What is asexual reproduction? Reproduction where one parent produces organisms that are genetically identical to the parent. Only one parent is involved and therefore is creating clones.
What are the advantages and disadvantages of Asexual reproduction? ADVANTAGES: It is a fast process and can rebuild a population quickly and only one parent is required. DISADVANTAGES: There is no genetic variation, which makes the species susceptible to changing conditions.
What are the advantages and disadvantages of sexual reproduction? ADVANTAGES: Genetic variation gives the species a greater chance of survival in changing conditions. DISADVANTAGES: Its is a slow process and and two parents are required.
What is cloning? Reproductive technology that uses genetic information from one parent cell.
What are the two methods of cloning? EMBRYO SPLITTING: an embryo at an early stage of development is divided into two smaller embryos (twins) SOMATIC CELL NUCLEAR TRANSFER: an unfertilized enucleated egg is fused with an embryo that contains a nucleus.
Why is meiosis important? Reduces the number of chromosomes from 2n to n. Genetic variation.
How do we get genetic variation? 1- INDEPENDENT ASSORTMENT - when homologous pairs separate, maternal and paternal chromosomes split randomly. 2. CROSSING OVER - exchange part of a chromosome with a part from the homologous chromosome. 3. RECOMBINATION - the production of new genetic information from the processes above 4. SEGREGATION - Allele pairs separate or segregate during gamete formation and randomly unite at fertilization.
What happens when mitosis fails? Nondisjunction occurs if a pair of chromosomes fail to separate at anaphase. Results in Gametes having a extra or missing chromosome.
How does fertilization occur? INTERNAL FERTILIZATION - Occurs inside the body of the female. the chances of gametes meeting is much higher then external fertilization. EXTERNAL FERTILIZATION - Occurs outside the body in the external environment. Requires a large amount of gametes so there is a lot of wastage.
What does Antenatal development require? (Antenatal = pre-birth) 1. single zygote is formed when the egg is fertilized by a sperm 2. mitosis occurs to turn the single zygote into billions of cells 3. cell differentiation occurs to produce over 200 different types of cells. this takes approximately 40 weeks.
How does an Embryo form? ZYGOTE - formed by a single sperm and egg EMBRYO - formed after the first mitotic division of the zygote. BLASTOCYST - a hollow fluid filled structure which has an inner mass of cells surrounded by an outer layer of cells.
What is gastrulation? A complete cell migrations that are re-organised the inner cell mass of the embryo blastocyst into a three layered structure: ECTODERM MENSODERM ENDODERM each layer is composed of cell stem cells.
What are the key stages of embryonic development? In the first eight weeks: -organisation of cells into the three primary germ layers. -formation of the front-back and head-tail axis -cell differentiation and the formation of tissues, organs and systems.
What are stem cells and what are the different types? Undifferentiated precursor cells that have the ability to differentiate into many different and specialized cells. Stem cells are organised into their potency: TOTIPOTENT -all types of cells PLURIPOTENT - many cell types MULTIPOTENT - closly related stem cell types OLIGOPOTENT - a few stem cell types UNIPOTNET - only cells of the same type
What are the sources of stem cells? 1.EMBRYONIC STEM CELLS - obtained from the inner mass of the blastocyst. 2.PARTHENOTES - obtained from unfertilized human eggs that are artificially stimulated to begin development 3.ADULT STEM CELLS- obtained from various sources from inside the adult human body (bone marrow, skin, liver, brain etc.) and are multipotent 4.INDUCED PLURIPOTENT STEM CELLS - Obtained from certain adult stem cells that can be genetically programmed to return to an undifferentiated embryonic state.
What is abnormal embryonic development? Congenital abnormalities or birth defects are those that arise during antenatal development. Occurs in approximately 3% of births. Caused by genetics, environmental and unknown factors.
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