Development and genetics
• Are you curious about the
process of early development
of the body
Source?
Development and genetics
Process
Development and genetics
• An significant hormone named
HCG play an important role in
the process of the growth : it
keeps the corpus luteum
functional in the ovary to maintain
the endometrium .
• The presence of HCG in the urine and
blood is the basis for pregnancy tests.
Development and genetics
• An significant hormone named
HCG play an important role in
the process of the growth : it
keeps the corpus luteum
functional in the ovary to maintain
the endometrium .
• The presence of HCG in the urine and
blood is the basis for pregnancy tests.
胚胎的发育
During development,the fetus is nourished by the
placenta,an organ formed form the outermost layer of
the embryo,the chorion,and the innermost layer of the
uterus,the endometrium.
在胚胎的发育中，胎盘滋养这胚胎。器官形成于子宫的
外膜，内膜和绒毛膜
Here ,exchanges take place between the
bloodstreams of the mother and the fetus through
fetal capillaries.Fetal blood in need of
cleaning,oxygen,and nutrients is carried to the
placenta in two umbilical arteries,while restored
blood is carried form the placenta to the fetus in a
single umbilical vein.
• 在胎盘里，母亲和婴儿通过婴儿的毛细血管里血液
的流动进行物质交换。胚胎里的血液需要更新，氧
气以及营养物质，这些物质都是通过两条脐动脉运
输，而贮存在胎盘里的血液则有一条脐静脉完成。
All three vessels are contained in the umbilical
cord.Although the two bloodstreams do not mix,and
all exchanges take place through capillaries,some
materials do anage to get trough the placenta in
both directions.
• 三条血管都包含在脐动脉索里虽然动静脉
系统并不混淆，所有的物质交换也都发生
在毛细血管中，但有一些物质却可以双向
的通过胎盘。
For example ,some viruses,drugs,and other
harmful substances are knowed to pass form the
mother to the fetus,and fetal proteins can enter the
mother’s blood and immunologic reaction.
• 例如，一些病毒，毒品以及其他的有害物
质可以通过母体传递给胎儿，还有一些胎
儿的组织蛋白也会引起妈妈的过敏反应。
The length of pregnancy is calculated
as approximately 280 days or 40
weeks form the LMP.
Childbirth, or parturition, occurs in
three stages:1) onset of regular
uterine contractions and dilation of the
cervix; 2) expulsion of the fetus; and 3)
delivery of the placenta and fetal
membranes.
从最后一次月经算起，孕期大约是
280天或者说是40周。
足月分娩分为三个阶段：
1）定期发作子宫收缩和扩张宫颈
2）排出胎儿
3）交付胎盘和胎膜
During gestation the fetus is
cushioned and protected by fluid
contained in the amniotic sac.
在妊娠期胎儿是被羊膜囊
中的羊水保护和缓冲的。
This means the
production of a
viable infant
regardless of
whether the infant
is alive at birth or
whether the birth
is single or
multiple
这意味着一个可行的生产婴儿无
论婴儿是否活着出生或出生是单
个或多个
Chromosomes and Genes
• The nucleus of each
germ cell contains
chromosomes composed
of DNA ,on a protein
framework.
• Each cell contains
thousands of genes , and
each gene carries a
specific trait , i.e. , “Each
gene is coded for a
specific trait .”
• The three types of traits
so carried are physical ,
biochemical and
physiologic , and they
thus influence an
individual’s physical
appearance ,
physiologic makeup ,
and susceptibility or
tendency to contract
certain diseases , as
well as the activities of
all the cells .
Ovum and Sperm
• The human ovum and
the human sperm
each contain 23
chromosomes.
• When the sperm
unites with the ovum ,
the fertilized ovum
contains 23 pairs of
chromosomes , or a
total of 46 .
• During cell division , the
chromosomes duplicate
themselves, so that new
cells thus produced contain
the same number and kind
of chromosomes as original
( a process usually termed
meiosis such that each
sperm or ovum receives
only one member of each
chromosome pair)
• One pair of chromosomes—-the sex chromosomes, which
determine the sex of offspring—-is very different from the
other 22 pairs ; the female pair has two similar members
called X chromosomes. whereas the two members in the
male chromosome differ from each other and called the X
and the Y chromosomes.
• Each male germ cell contain either an X or a Y
chromosome; if the sperm has a Y chromosome the infant
will be male; if an X, it will be female.
father
Ychromosome X chromosome
the chances of being a boy
or girl are 50-50
twins,triplets and quadruplets are much rarer in humans
than in most other mammals
identical and dissimilar
identical
produced from one ovum and one sperm
dissimilar
produced from separate ova that are fertiliazed
by different sperm
Gene function
——Manufacture of enzymes
•
Remember that DNA--the genetic material –controls the formation Of RNA
（ribonucleic acid）,which in turn spreads throughout the cell and controls the
manufacture of both structural proteins—the main components of skin, muscle,
etc—and enzymes –the proteins that promote all of the chemical reactions that
take place in the cell.
enzymes
Structural proteins
( skin.muscle.etc )
• Genes are said to be dominant or recessive :a dominant gene is one
that expresses its effect even in the presence of a different (recessive)
gene for the same characteristic
A
（dominant gene）
＋
Aa
(Express the characteristic of A)
a
(recessive gene)
Gene mutation
•
As a rule, chromosomes replicate exactly during cell division ,
occasionally , for reasons not yet clearly understood ,there is a change in
the number of chromosomes ,or chromosomes somal breakage ,in which
there is loss of or rearrangement of gene fragments ,resulting in genetic
mutation
Do you think gene mutation can lead to these
phenomenon ?
• the mutation occurs in if an ovum or a sperm involved in
reproduction ,the altered trait will be expressed in the offspring.
( mutation occurs in an ovum or a
sperm involved in reproduction )
唐氏综合症
• The vast majority of harmful mutations are never expressed because the
affected fetus dies and is spontaneously aborted; and most mutation are
so inconsequential that they have on visible influence .beneficial
mutations tend to be spread throughout a population.
图16 无脑畸形伴脊髓脊柱裂
vast majority of harmful mutations
affected fetus dies
组长：徐晓钰
成员：赵娜娜，夏菲，王婷婷，周政，周洋，叶川，张亮，
周志国，尹可辉